If you, for example, have a recurring service transaction for which tipping is appropriate, you may end up with two charges: one for the service itself, and another for the tip.
It would be ideal then to be able to make some semantic connection between these two charges. Typically the tool for doing so in LM is groups.
But you cannot add a transaction that is recurring to a group of transactions. It would be great to lift this limitation, as from a data model perspective there shouldn’t be a great difference between a standard transaction and a recurring one: the latter presumably has a many-to-one relation with some “recurrences” entry (or this information is denormalized) but is otherwise the same as a normal transaction and could as well have a many-to-one relation to a “group” entry.