How to change "build-modifier" keys?

[Skasi]

Where can I edit the keys used for things such as "box-building" (alt+shift), "line-building" (ctrl+shift), etc.?

[Beherith]

uikeys.txt

[Skasi]

What do I have to type there to rebind Alt+Shift to AltGr+Shift?

[Skasi]

I still need to know how to do that. *most cutest voice and expression ever*

[knorke]

in rts\Game\UI\KeyBindings.cpp I see nothing related to rebind the box/line/hollow box hotkeys, only buildspacing.
Might be hardcoded like some other keys.