Oh. Endgame mode just means making the LCARS colors like those from the future in VOY: Endgame
. Here's the standby screen showing the VOY, INS, and NEM themes, plus the VOY theme in Endgame mode.
Another, more obvious, case of giving meaning not seen on-screen is just having the inline digits of buttons represent key labels, which seems so natural when you see it that it's easy to forget that in Trek they just looked like random digits. In the case of brackets, as in the screens shown above, they are divided into boxes, and each one has a key label so the user knows what key to press to activate something.