You can always enter tags manually in the "Properties" section using the "+" sign.

E.g. for a salt marsh, the wiki names the right tags:
https://wiki.openstreetmap.org/wiki/Tag:wetland%3Dsaltmarsh

If you have question about tagging, the best place to ask is the forums - maybe show an example and ask for tagging suggestions.
https://community.openstreetmap.org/