Can't find "Lengthen Duration by..." menu items

Key Commands are offered to Lengthen Durations by specific values. (eg. Lengthen Duration by dotted 16th note). But the menu items under Write → Edit Duration → only offer Lengthen/Shorten Duration by Grid Value, not by another specified value.

Are those menu items hidden somewhere else (that I can’t find) or are they only available via the chosen Key Command keystrokes? (Searching for shorten or lengthen only highlights those grid-related menu items).

I think they’re only available by using custom key commands.

Also available via the jump bar.

Yes, of course!

Thanks to both of you. I was hoping to unify a bank of commands like this in a Keyboard Maestro macro palette directly accessing menu commands. It will still work, but only by invoking corresponding Key Command keystrokes.