Multiple Displays: Restrict mouse to single display

The only solution I'm aware of is EdgeCase, which doesn't look to have been updated in 8yrs. This seems like a natural fit for BTT.

Basically, it keeps the mouse cursor on a single display, reducing the risk of "losing" the cursor, especially when secondary monitors are used for video/presentation (cursor not visible). The mouse can cross over simply by holding a modifier key (e.g. ⌘)

I had a similar issue about two years ago and managed to find a workaround. It actually worked quite well, and I rarely encountered any slip-ups.