Finding Index of Gameplay Tag with child and change it.

Note that this is not about Actor Tags.
I am trying to find the *index *of a Gameplay Tag with children and change the child.
For examples sake, let’s say the tags looks like this: A.A, A.B and A.C. In addition to those tags, there may be more tags both before and after the parent A. I want to change the tag, whatever it may currently be, to A.B for example. (by finding the *index *and the node Set Array Elem).
Setting the value using Set Array Elem works, but I am having trouble finding the correct index, nor am I able to find a Gameplay Tag node that allows for modification, apart from *append *which does not seem useful.

Note that *Contains *did have A selected while testing.

Maybe I am missing something?
The only thing I can think of now is doing a big mess of Does Container Match Tag Query, Compare Tag Container to Other Tags and branches to get which child it is, then array find to get its index.
And that doesn’t feel like a good solution since there may be many many more children tags of many parents.

It would be super useful to have a node that returns the child of a tag, or a node that allows for changing or add/removal of a tag, if there isn’t already and I’m missing something.