Unfortunately, there isn't a way to filter songs where you can do something like say, "Only synchronize songs that are a part of this collection or setlist", or "only filter songs that are newer than this date". The tool is designed to keep libraries completely in sync (meaning all songs are considered), but it lets you choose to ignore synchronizing types of data such as annotations. A future enhancement couldn't certainly add complex filters like that, but it won't be part of the initial release.
Having said that, one thing you can do is change the merge behavior which may give you enough control to do what you want. You could use the "prompt" behavior so that you can choose what actions to take for every song in the library that is different. If there aren't that many differences, then it wouldn't be too tedious. If you have a lot of songs with a lot of differences, then you'd have to spend a fair amount of time tapping the "skip" button to get to the songs you do care about. If you are only merging new songs, there is a behavior for that, so it would be quick and easy.
I'm always open to feedback for suggestions on improvements if they will be useful to a lot of people.
Mike
Having said that, one thing you can do is change the merge behavior which may give you enough control to do what you want. You could use the "prompt" behavior so that you can choose what actions to take for every song in the library that is different. If there aren't that many differences, then it wouldn't be too tedious. If you have a lot of songs with a lot of differences, then you'd have to spend a fair amount of time tapping the "skip" button to get to the songs you do care about. If you are only merging new songs, there is a behavior for that, so it would be quick and easy.
I'm always open to feedback for suggestions on improvements if they will be useful to a lot of people.
Mike