Add default shortcuts for intervals below

Better get into the habit of building your chords bottom to top.
Or use Shift+'notename',Ctrl+down to enter and then lower by an octave or use Shift+'interval'

See also #45171: Note entry using Shift+letter appears unpredictable

Yes, for now, enter using Shift then Ctrl+down is the way to go. But I agree there should be a separate command for adding below. Probably we wouldn't be able to assign a shortcut by default (they are in short supply), but I'm guessing most people tend to want to build chords either top down or bottom up pretty consistently, so you could just redefine the existing shortcuts if the commands were available. Or, a preference to control behavior of the existing command, although that's probably not as clean a solution even if it might seem more intuitive to some.

If this is about intervals, those commands already exist—they just don't have default shortcuts.

Yes, I should have made clear I was talking about the note (letter) shortcuts. I'm proposing essentially the same model for these as for the "interval below" commands - we could add the command, let user decide if he wants to switch the shortcuts over from the "above" commands to the "below" commands.

Shift+Interval is wrong, sorry about that. But there are shortcuts available for interval above (and they default to Alt+interval) and interval below (they are not set, so you'd need to set them yourself, e.g. to Shift+Alt+interval

The commands are already there, you just have to define shortcuts by yourself.

I'm aware that there is concurrency in shortcut-land; but this request has come up a few times over the past year (mostly from Sibelius users) where the functionality often isn't discovered as easily as it could be.
So my vote would be to add Shift+Alt+number (Shift+Option+number for Mac) as default shortcuts for these actions.

EDIT: side remark from Marc's memory and confirmed by me. The proposed shortcut would work with numpad keys; but not with the top row keys for AZERTY keyboard users (where Shift+symbol == number)

As I recall, we had those enabled in MuseScore 1.0 but remove them not too long after once it was realized they weren't compatible with AZERTY. But, that was before we had the ability to select different shortcuts cuts by keyboard layout. So we could consider consider adding these to the QWERTY layouts only, and perhaps substitute something else for AZERTY.

First of all, I'm all for this! I would just add to this my other previous suggestion (added to the issue tracker, link included here), which basically would let you use the exact same shortcuts already in use, but have a "direction switch" hotkey.
https://musescore.org/en/node/308938