Hey. I changed ToggleInventory and GUINavNextGroup parameters in ini file so I can open and close inventory with Tab button, but the problem is that when I click on something in inventory, Tab button starting to switch between elements there. Is there way to fix this? Am I asking too much?
Just guessing, but it sounds like you just want to be able to open/close your inventory with TAB, which ToggleInventory should do. If GUINavNextGroup cycles through the elements then obviously you can’t use the TAB button there too or you won’t be able to close with TAB. You either need to change it to another hotkey or use ESC to close your inventory.
By the way, welcome to the forum! 
I changed ToggleInventory to TAB which is already enough to open/close inventory, since is toggle. Then i changed GUINavNextGroup to “I”, so it doesn’t conflict with TAB. But the whole thing works only until i click on something in inventory, after that TAB starting to cycle WITHIN elements in inventory, not the categories above. How to fix that? I mean is it really that hard to allow players choose hotkey for inventory? Is TAB in most of such games. But no, here we’ll cycle you through every single cell in your interface for no reason.
Sorry, 
the short answer is to wait, because Funcom is changing most of the UI and hotkey funtions as well as resetting all the keybinds in the process when 3.0 drops. Best of luck.