That's not straightforward =)
I could not figure out and had to resort to searching.

#OpenStreetMap

@richlv I had this experience last night but in reverse. I was searching how to move something with JOSM.
@richlv For what it's worth, iD has an overview of all its keyboard shortcuts built in. It's 'M' for Move.

@uneabeille Oh, JOSM probably has all kind of built-in help, I just went with discoverability :)

What did you try in JOSM that didn't work, BTW?

@richlv The worst for me in JOSM was trying to figure out how to scale an object. It ended up being a three-button shortcut. 🙃 It wasn't under Tools or More Tools in the menu. The sidebar said I was already in the right tool. Eventually I gave up and looked it up.
@richlv I also couldn't figure out how to add a pedestrian area, so I had to look up the tagging default from iD and enter it manually on a way.