Using multiple open projects in Logic Pro X to be a midi music player

In Logic Pro X 10.4, I’ve been using multiple open projects to play midi accompaniments as a playlist by switching between their windows. I’ve run into problems with this solution in 10.5. For example, the project playback appears to get mixed up about which open project’s channel patches are to be used by the front project.

I know that it’s possible to make set lists in Mainstage 3, but that appears to require converting to audio, and I want to retain midi editing capability for each project.

Is it possible to combine maybe 10 or 15 projects into a single project in linear alignment so that they can be navigated for playback using markers without losing or misaligning any of the unique information belonging to each project? I’ve not found a way to use “import” that keeps the imported project playback data and puts it at the end of the existing project time line. I may be asking for a sort of beefed up version of the Arrangement feature, the way the old Studio Vision Pro app let you handle sequence steps by designating a letter for each sequence in a song. Thanks.