File save can't determine file type without extension
Many programs allow typing the name of a file without a file extension, and then allow a corresponding drop-down box for file-type to dictate the extension to the operating system without forcing the user to explicitly type the .extension. Musescore, however, won't save a new file without typing in the extension.
I.e., if the user types "my_file" without an extension, even though the extension drop-down box says "MuseScore 3 file", it won't save and grant an error-message. This should be fixed, as it is a minor annoyance. It's not major, most definitely, but it should be fixed, and this should apply for any file-type selected in the drop-down list without requiring explicit typing of the user. Same goes for exporting.
Interestingly, this doesn't seem to have been mentioned at all (I think it's easy to disregard the problem and not mention it since it's not a big deal).