How to save a music sheet in Musescore

Once you have selected a folder and filename - which happens the first time you save a score - subsequent save operations for that score simply save to that same file. This is standard for virtually all Windows, macOS, and Linux programs. If you're looking for confirmation that something actually happened, look at the name on the tab right above the score itself (below the toolbar). If there are unsaved changes, you'll see an asterisk ("*") after the name. Upon saving, the asterisk goes away, returning as soon as you make another change. Again, this is standard behavior in almost ll programs.