I need to put in a bunch of tempo markings (rit, etc), and I have a video with audio with the score already synced exactly (with extensive edits in the tempo track). Will putting in these markings override anything I already have?
I suspect they will, but you should be able to use the suppress playback property to prevent that happening.
If you already have appropriate tempo markings in the Tempo track, then they will be appearing in the score itself as signposts; another option would be to change their properties such that they actually appear.
I don’t want the tempo markings to appear in the score for the live players, but I do want the mockup to exactly follow the tempo track. I didn’t end up needing that many markings, so I did the suppress playback thing.