I probably won't be able to add action triggering to show things like HUDs in scroll modifiers, that doesn't fit well into the architecture and would make them even more complex and potentially slower.
To see whether a condition becomes true you could configure a separate "Trigger On Change Of Advanced Trigger Conditions" trigger in "Automations, Named & Other Triggers".
If the position and size of the tab list is always the same in the window you could maybe use dist_x_active_win_top_left which gives the mouse position relative to the window (I don't have Edge installed right now)