For what i saw, it only uses a Data Table with the ThrowGrenade row, not the brush key set.
I have found a brush key set entry in /All/Game/UI/Foundation/Platform/Input/KeyboardMouse/CommonInput_KeyboardMouse, but i cannot find it used anywhere
It is using the data table row, which is assigned to a single key (Q in this case) and in the Common Input Base Controller Data, there is not a Input Brush Key Set for the grenade, so it uses the Input Brush Data Map for the Q button
I recently set this up to display a WASD icon using Input Brush Key Sets, so here’s how I got it working. Note that I’m not using the Enhanced Input Support with CommonUI.
First, create a CommonUI Input Action Data Table and define your input actions there:
The Action Widget on the right (green square) has multiple Input Actions assigned. It will automatically look up the corresponding icon in the Input Brush Key Sets and display the combined brush (for example, the WASD icon).
The widgets on the left are just showing the regular single-key icons via the Input Brush Data Map. For them to show you need to configure the Input Brush Data Map.