Hey @dbw, welcome to the forum!
You’re right: at the moment, when importing songs into a larger setlist project, Song Start / Song End locators still have to be placed manually, and they won’t stay linked automatically when shifting the arrangement.
This is mainly because Ableton’s API doesn’t currently allow renaming or dynamically editing locator names, so AbleSet can’t automate that fully right now.
There has been previous discussion about defining Song Start / Song End using MIDI clips.
Here’s the thread where that was talked about earlier.
For now though, the current workflow is the supported one — but really appreciate the suggestion!
Agus