My sense is that you do this by checking the markers that are important and then finding the tempo with the least deviation for those boxes. You set one of those tempos for the section you are interested in. Your original tempo would have been set to arrive accurately at the start of the new tempo by checking/concentrating on different IMPortant markers so that everything works out.
Others with more experience working with this feature may want to chime in here to add to or correct my impressions.
My experience has been different so far – I set up a number of “important” markers in succession (say from bar 100 to 150), but the tempo marking changes went to the top of the flow… which was not my intention at all.
I’d enter the suggested tempo manually at the start of the selection I wanted.
I’m not surprised the Apply button applies the tempo to the entire flow/piece since some, perhaps many, users will call this utility to try to find a single tempo that hits (or almost hits) all their important hit points.
The find tempo dialog only works per flow basis, it can’t be really used on just a part of the flow. If the found tempo is inserted somewhere in the middle of the flow rather than at the start there is no guarantee that the markers will fall on beat (actually it’s more likely that they won’t).
that’s too bad – from a film-scoring perspective, anyway – and I hope it can be improved to handle excerpts than just the entire flow.
Reckon I could export a video of just the desired sequence into a separate flow and then copy-paste it back into the current flow score, but that seems more longwinded than just approximating the old fashioned way.