Interesting. I've been using MuseScore for a fair time, so know the shortcuts I use regularly and the odd quirks that I personally find.
It was frustrating watching him try to change the tempo as my immediate reaction was to check if it was still in note-entry mode ... it was. Click the icon top left or hit escape. I did wonder that he didn't set the tempo during the initial score setup ... he did most else, but skipped that.

Watching someone who didn't use the manual but brought knowledge and methods from elsewhere made for some discoveries for me ... I've always selected the note (or bar for some) and clicked the icon from the pallet ... I hadn't tried drag and drop to the note. Doh! However my way does allow me to select multiple notes and double-click the item to apply it to all.

He appears to have no discovered the rest is a note 0 (zero) or that one can enter notes by typing their letter. Probably he also hasn't yet discovered that Ctrl-UpArrow and Ctrl-DownArrow shift the note just entered by octaves. Just those few things make like much easier. I hate having to use the mouse too much ... I have some RSI issues as a consequence of doing that in the past.

Jazz relative beginner, starting at a much older age than was helpful.
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