How can I sync a regular file or package like the Photos Library?

SyncTime syncs the source with the destination, not with the file inside the destination that has the same name as the source. That’s why the source and the destination need to have the same type: they both need to be either directories, packages or regular files.

If you want to sync a directory, you can easily create one on the destination from inside the Open panel by clicking the New Folder button. If you want to sync a regular file or package, you need to copy it manually to the destination first so that you can then select it in SyncTime.