I just want a battle command window (Attack, Skill,
Item, Guard) that stays at the top left corner of the screen,
regardless of who's selecting their action. I don't want it to hover
over the status display of the character who's selecting their action.

It's normally like this:
I want it to be like this:


I tried replacing every "@actor_command_window" in
the "Scene_Battle" scripts with "@spriteset_command_window," but this
did nothing. Is there any specific "@xxxx_command_window" that would
achieve my desired result?

Thank you!

if you're not using any custom script that changes this, this is the line that cause the window movement
Just put an fidex value.
Also to change the y position just add bellow this:

Thanks! I'm planning to create a Lunar 2-esque battle window with the character portrait on the right.