do you have advice for making an innerworld when absolutely zero visualisation is possible?
i can't use any senses because the best i can do is weird pseudo-proprioception? y'know that trait some animals like dogs or insects have where movement is easier to see than still objects, yeah like that but i don't actually see anything
even then i can only imagine one thing moving at a time, imagining taking a single step would mean constantly flicking between my thighs, lower legs and feet as if watching an unfinished animation where some frames are missing limbs, which is a headache and a half and would mean having more than one system member present is either impossible or too difficult for me to want to bother
So it's seems like you've explored a lot of other senses and found the imaginative side of those lacking as well. That you have some level of proprioception is something you might build on. Normally we would suggest trying to build on that, but if they're causing headaches, well then that's not great and it might not be worth exploring.
However, you may try to explore it without movement. We teleoprt a lot around headspace. Instead of imagining what every limb feels like as we walk around, we jump to imagining what our body feels like in different sitting, lying, or standing positions. And we don't try to focus on all parts at the same time. Usually spending more time focusing on our head/faces or torsos.
But again, that might be something that causes more pain and doesn't work for you.
So instead, you might try bootstrapping!
First, a note about aphantasia to keep in mind. There's a difference between visualizing and knowing. A person can know what something would look like if it were in front of them. If I ask you to describe an apple, you could probably list off facts about what apples look like, even though you're not visualizing one. This comes from your real world experience of having encountered apples throughout your life, and recalling the knowledge gained in those experiences. We're going to lean heavily on this knowing to replace visualizing.
Think about your home (or somewhere else familiar). Remember where things are in relation to other things? Remember how if you were looking for the TV remote what places you'd try to search? When you brush your teeth remember where your toothbrush is relative to the sink? (These of course might not be universal, so do try to add your own personal routine experiences here).
If you're having trouble with that, try to take note of these things in your daily life. I think it's called being mindful, but tbh mindfulness is a concept that boggles our minds.
Once you've got that, when you can hold a spacial memory like that in your focus, try to take note of how that feels.
If you're remembering the specific times you've done those routines or been in those places: Try to mash them together to find commonalities. When you are in your memory of your bedroom, try to recall this memory from different times you were there (and especially from different angles).
The goal is to get to a point where you can remember these places as purely spacial. Not any specific memory of a time you were in a place, but rather the place itself.
This might sound like trying to visualize, but it's not that. It might be if you're like us, but there's a non sensory component to just knowing where some things are in relation to other things, and that's what we're trying to focus on. (Again, the visualizing vs knowing concept)
So, you have those memories? Now pick a room you like the best, that you feel strongest with. If you were in that room right now, where would you be? Or rather, where would you want to be? Just for the moment. Let's say you picked a bedroom. Would you be sitting on the bed? Lying down? Maybe standing in the doorway? Perhaps you have a chair and a desk that you could sit at?
Now, where would some other things be in relation to where you would put yourself? Think about those other places in this room. If you're on your bed, where would the doorway be in relation to you? If you're lying on the floor, where would the desk be?
Once you've gotten comfortable with that, ask your headmates where they would like to be in this recalled room. They might pick the same spot, and that's okay. If they pick different spots, share with each other the spots you picked. Tell your headmate where they are in relation to you, where you are in relation to them, and ask them to do the same.
Then practice doing this. Get a really strong idea of where these things are. As you get more comfortable ask yourselves about what kind of things you might be able to feel from these places. Think through what you might be able to see if you were sitting in the chair vs in the bed. This won't be imaginative as much as it will be deductive. If you don't know the answer, try to go to that place physically and observe what it is you can see/hear/feel from there. As you practice these questions will likely get easier for both you and your headmates.
Now to get a bit more predictive. If you and your headmates have pictures of yourselves, ask each other and think about what it would look like for you all to be in those places. Again, this won't be imaginative. You won't be conjuring an image of all of this in your head. Instead try to think of and answer questions about what would be true if you all were there. Let's say Headmate A is at the desk and Headmate B is on the bed. Could they see each other from there? How much of the bed does B take up? What part of A's body is parallel to the top of the desk? Are either within reach of the other?
This step might be full of stumbling blocks. Just remember, it's okay to get it wrong. You're trying to make deductions and guesses about things that aren't readily available to test. There will be times when you didn't take into account someone's height, or their wing size, or how far apart the walls are, or any other myriad of information that you're just pulling from faulty, limited memory (as we all are). Taking notes or drawing might help.
The other major stumbling block is to get too caught up in the idea that this is imagination or that you should be getting some sort of visual output. You likely won't. We can manage to pull visual information from memories, but as soon as we try to edit them they fall apart and turn into black void. But what this technique is trying to do is just work past that void. These are simply theoretical facts about the spacial relationships of things, headmates included. They're "what ifs".
Keep practicing. The more you repeat these facts, think through these questions, and recall these spaces, the less thought you will need to pull them up.
To make this a part of your inner world, well, if you've gotten this far you more or less already have. When you want to "go" to your inner world, focus on that place. Ask your headmates to be there. Ask about those details. Think about what it would be like to be in that room with them. Directing more of your attention there and less on the world around you will catalogue your memories as being there rather than wherever it is your physical body actually is.
But, say you don't want this room, and instead want a place you've built yourself with a fully customized shape and feel. Look for creative games. Stuff like minecraft or the Sims. Turn on creative mode. Build a house there. Explore it a lot. Get very familiar with it. Then try these exercises with that location. Whatever creation suite you choose will have its tradeoffs, so pick whatever feels most comfy (hell I'm sure that CAD software would work for someone somewhere).
When you wish, you can add to these places. Repeat this process with another place. You can "get back and forth" with a sort of teleporting. Which is just doing this deductive work between headmates in relation to a different room. Instead of asking about what it would be like to both be in the bedroom, ask what it would be like to both be in the kitchen.
Or you can attach these places with further questions. Add a door to each room that connects them? Well how does that work? Which way does the door swing? How close to the ceiling would it go? What color would it be painted? (These questions are yours to answer, i.e. make up)
Or instead you can redirect doors and windows. When one headmate is in one room and another is in the other room, what would the sounds be like? How much do the walls muffle the sounds? Which walls are shared? Do they intersect with each other in non Euclidean ways? (Again, you can just make up answers)
The extra step to these last two additions will require some degree of reinforcement. You will need to repeat the answers to those questions. These new rules and made up interactions will only have your collective memory to verify or answer. (Although writing these things down or plotting them out in a creative game will help).
Getting into headspace, or creative with it is very difficult when there's nothing there to see. I hope this helps!