EDIT

Copied from #8146:

Generally it should be possible to move a Character subtree to a Feature tree as Character is a subtype. But of course then all term nodes need to change its term type to the more general term type "Feature". We have discussed this already on cdmlib level for the "add" method. Please open a new ticket for this issue as probably it is not simple enough to be implemented still in this ticket.

Also the other way round we need to discuss. Feature nodes may be moved to character trees if and only if all the feature nodes contain characters. This is important to make the operation reversable. But it requires an additional check if the condition holds and user feedback if the operation is not possible.