Sorry for the delay in responding - I’ve just gotten back from some travel.
What you propose seems to me to be the simplest & easiest way to do it, but of course, others may have other / better ideas! I’ll unpack this a bit more below, but let me briefly mention one other alternative: You could create a single .mlt file with all of the video and audio, syncing up each as needed. Then you would pull that single .mlt file in as a source, and drop the desired pieces of it (set the in and out points for each use of the file) into the timeline as needed. Would there be any advantage to doing it this way? Someone might find it easier to have a single “synced” file to work with rather than multiple files … personally I would find this less convenient, but I mention it “just in case.”
More thoughts on using 7 different .mlt files: To make this work really well, I would suggest giving some advance thought to how you are going to set up a file structure that will help to organize everything. To be honest, this is a place where Shotcut is a bit weak; it doesn’t really have much in the way of project / file management.
When you open up Shotcut, it asks you to choose an existing project or to set up a new project. For the latter, it assumes that you want to create a new directory with that project name, and then put a .mlt file with that project name in that directory. Not an unreasonable default action … but not always what you want. Say for example that you want to create 7 .mlt files in a directory called “Synced Clips,” with each .mlt file having a particular name, maybe something generic such as “Sync1.mlt” and “Sync2.mlt” and so on, or maybe something descriptive such as “Waterfall.mlt” and “Rainbow.mlt” and so on. The initial-screen project system does not lend itself to this scenario.
BUT - though it was not entirely obvious to me as a new user, it turns out that you don’t actually have to use the initial project screen. You can simply start pulling in files to the playlist or timeline, and you can “Save as” using any directory and name that you want. You can open an existing project (using the initial project screen, or just by using File:Open), modify it, and Save As to put it in a different directory or under a different name.
BUT - here’s a bit of a catch I have run into. More than once I have assembled files for a project, and they have gotten all jumbled up in a directory. I have decided that it would help to structure the files into subdirectories to make it easier to find things. I want a subdirectory called “Raw” to store all of the raw / unsynchronized clips; a subdirectory called “Synced” to store the synchronized .mlt files; and a subdirectory called “Final” to store the final .mlt file and export(s). But Shotcut does not really have a project management capability; the only thing you can do within Shotcut is a bunch of “File:Save As” operations … which is going to result in multiple left-over files in one directory after I save-as the files to a different directory.
Of course, I can easily create directories and move files around using my OS. But if I do that, the next time I open the project(s) in Shotcut, it can’t find the various source files, because they are no longer in the same place they were before. There is a fairly basic mechanism that attempts to help you find the missing files; it requires opening each project and going through to find the new directories for the different files, then saving the result. It works reasonably well, and it is not the most onerous thing to have to do … but it will save time and energy if you plan out the file structure BEFORE you start creating .mlt files, rather than after.