Don't think this is possible, unfortunately. Unless there's a "pause" key that I'm not aware of that doesn't pop up the menu.

Which isn't a problem most of the time since it's turn-based once combat starts. I'm guessing you're trying to edge closer to enemies so you can start combat on your terms, but they keep moving and messing it up for you? I've been in that situation, it's kind of annoying.

At first, I've found it's best to get almost close enough to fire, but then only move closer when they're moving away from you. Either that, or get to almost-in-range when they're moving away from you, and then get ready to fire as they turn around and head toward you again.

After a while this became a non-issue due to a combination of higher stealth and better range on weaponry - at that point you can just calmly walk to within range and fire whenever you want (although it can still be annoying clicking on them when they're moving).

Thank You,

Sweet!