And pressing Cmd+Enter (or windows CTRL+Enter) in a text field is a brilliant trick. I discovered it after 9½ years of Photoshop usage :)

That’s the “funny” thing about Photoshop – it’s loaded with hidden shortcuts!

Applying it to a web form is an interesting idea, however, I think the combination of an input field and a shortcut key requires an unrealistically skilled user (referring to your last observation) :)

Perhaps a contextual menu shown only when the field has focus is a better solution? (Almost like those date input fields where you pick a date from a popup calendar).

By the way, did you know that you can press Cmd+Enter in order to deselect the current text field? Normally you need to switch tool, when you are done using the text tool.