I'm also a fatigue-and-pain occasional power chair / motorized grocery cart user, and one of the petty problems I have is skirt management. I have to be careful that my long skirts don't get variously fouled in the wheels or drag on the floor. A floating chair would eliminate the wheel problem, but depending on the height at the moment, if your character has dramatic sweeping or floaty clothing, it would be useful to have something that would keep any trailing ends from getting dirty on the floor/ground, and from catching on any obstacles. While still looking cool.
Storage space, and an easy way to get stuff out of there. (Sounds easy enough with terrakinesis, you could have metal that opens at will but is otherwise sealed, and your character can form a custom grabber out of the metal to hold the object in the exact correct place. Which might wind up looking a little bit Doc Ock?;) ) It's up to you whether you want to have the storage space accessible by anyone other than your character - if it's not, what happens if something important is in there while your character is knocked out or asleep; if it is accessible, would theft be a problem in that circumstance?
Custom colors/patterns, of course - some wheelchair users like to put stickers on, I got my power chair used and it's not the color I would have picked, and I repainted my first rollator. Light-up bits would be cool, depending on personality.
If your character is picking an office chair out of commercially available office chairs, they may wind up completely replacing the cushions with something custom, due to what alias_sqbr mentioned -- pressure sores and related ergonomics are definitely an issue for paraplegia, and IRL wheelchair users have died of injuries related to sitting in an unsuitable chair for extended periods of time. (I'm thinking about a specific case of someone whose power chair was destroyed by an airline and she was abandoned for hours in an airport transport chair without regard to her specific limb situation.) So a cool feature would be some kind of anti pressure sore / DVT motion, which could be powered by active terrakinesis but for their health ought to be something automatic built into the chair, so they won't accidentally forget it and have their health suffer for it. But office chair wise, you probably would not want an office chair rated for less than 18 hours' sitting, and at that point you're getting close to wheelchair budget. But with an active community of terrakinetics, there are probably like message boards based around materials hacking, and your character might devote a year or two of their previous life to extensively customizing their chair with input from their medical team.
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Storage space, and an easy way to get stuff out of there. (Sounds easy enough with terrakinesis, you could have metal that opens at will but is otherwise sealed, and your character can form a custom grabber out of the metal to hold the object in the exact correct place. Which might wind up looking a little bit Doc Ock?;) ) It's up to you whether you want to have the storage space accessible by anyone other than your character - if it's not, what happens if something important is in there while your character is knocked out or asleep; if it is accessible, would theft be a problem in that circumstance?
Custom colors/patterns, of course - some wheelchair users like to put stickers on, I got my power chair used and it's not the color I would have picked, and I repainted my first rollator. Light-up bits would be cool, depending on personality.
If your character is picking an office chair out of commercially available office chairs, they may wind up completely replacing the cushions with something custom, due to what