I believe it used to be that when the inline interlinear is in current use that there is a box around the symbol in the bible Resource Toolbar. Now the box only shows when the symbol is clicked on, presenting the choice to check to turn the interlinear on or off, then the box disappears. I liked that indicator, though I can see by looking at the bible text whether the interlinear is on or off.
The interlinear symbol for opening an interlinear pane at the bottom of an interlinear bible still shows an outline box around the symbol when the interlinear pane is open.