Both these approaches seemed to work well for me using H19.
- Open Take List and left-button drag some take onto Main. A pop menu allows to pick "Merge take (with override)".
Simply "Merge take" is not enough as both Main and the unwanted take has values for the same channels. - In a Textport window: takemerge -f Main <name-of-unwanted take>
Again it's the -f that does the trick of forcing the merge even though it means overriding Mains animation channels.
Once merged, I just delete the unwanted take.