Therein might be your solution --- see if you can find out how they
are "push-pinning" (aka going "modal") their screens. Maybe they can
tell you how to include your Excel WB in their set of modal windows so
that your WB will get the same treatment.

BTW, I earlier used the wrong term. I suggested clicking the Excel WB
app button on the 'menubar' -- I should have said 'task bar' (the
thingy at the bottom of the screen). Apparently, pressing ALT+TAB will
do the same thing.