Unfortunately the "ad-hoc" break was something that has been on my list for a long time but never made it in as a feature ... at least not yet.
My recommendation would be to have a break either at the start or at the end of your tournament, and when you need to have an ad-hoc break go to the Rounds tab and right-click on that break and select "Set as current level". After the break you'll have to set the level back to the current round the same way. Of course, because the level will be incorrect, the "next" values also won't be correct (next round, next blinds, next ante, etc). That may not be a great option.
Another solution would be to create a "break" screen, separate from your other screens. Pause the clock then switch to the break screen (you can select any screen from the Controls page or by default the keys 1 through 9 are hotkeys which will switch to that screen). When you switch to a screen using the Controls tab or the keys 1-9, it will automatically engage the screen lock on that screen. You'd have to keep your own time on your ad-hoc break (if you are keeping time during this type of break) and then simply disengage the screen lock (Ctrl+L or the Controls tab) to return to the usual screen.
I thought there was a way to do this using an Event but there is no action to change the currently displayed screen. I've added that to my to-do list.
