Templates too limited
I would like to be able to be more specific in setting up my user templates. In my case I would like line breaks to be all set up (4 bars per staff) filled with slashes for 32 bars. I know the work around (opening a file set up that way and then "save as") but it would still be simpler to open up a template with everything in place as desired.
The start score whenever you open up MuseScore is pretty close to what I have in mind. Why is it possible for that particular score to have the line breaks in place but I cannot save a user template that way?
True, templates capture only the basic structure of the score, not any content (such as notes, dynamics, or system breaks you've added.
The start score is not a template, it's simply a regular score loaded at startup. You are certainly welcome to specify your own score to load at startup instead - in Edit / Preferences / General. But you'd still need to "save as" to avoid overwriting it. Given that it takes but seconds to run the commands to add/remove systems breaks and fill with slashes (you can even define keyboard shortcuts for them in Edit / Preferences / Shortcuts, so it would be literally four keypresses*), I'm not sure it's worth the trouble or risk of overwriting.
*Once you've defined the shortcuts - say Alt+\ for fill with slashes, Alt+Enter for add/remove systems breaks - try Ctrl+A, Alt+\, Alt+Enter, then finally Enter to run the command.