I am trying to find the xml file, if it exists, that manages the window presented after right clicking an empty spell gem. It's the options dialog that appears after right clicking an empty spell gem so that you can select a new spell.
I've gone through the list EQUI_*.xml files a couple times and nothing is sticking out for me.
I checked out EQUI_EQMainWnd.xml which I believe is the file you are referencing. This managed the cascade window for the 'EQ' button but does not effect the 'spell select' window. I'm not trying to modify what is presented, but only enlarge the fonts.
My assumption is the window presented with right clicking on an empty spell gem is the same window presented when right clicking on chat or right clicking on a window to set the 'background' / 'alpha' / 'arange.'