Yeah, it's made more for refining and confirming details than for adding entirely new objects.

When I want to add something that's not on the map yet, I either add a note in StreetComplete and come back to it later on my computer, or I add it using Vespucci. (I've been known to add items using Vespucci, then reload the data on StreetComplete so I can fill in details that aren't in the presets and that I can't remember how to tag manually!)