Can I search for a tag/key/option e.g. barnvagn and then tag all those segment that contains that info with ramp=yes in some easy way?
Yes.
First use the Search (in Selection Dialog) to select all objects you want. In your case you want to search for “barnvagn:yes”.
Next just change/add/delete the properties accordingly. JOSM update all objects selected when using the property dialog.
Hmm That’s very nice.
Slightly related I usually just tag about ~15 different tag/key combinations, is there some way to save these ones directly in the history… (Oh this is a feature request)…
Yep.
Increase the priority, if you are impatient.
Ciao, Imi.