I'm trying to work out how to make something akin to a delta from rivers and I'm having a really hard time doing so. Is there a way to do them?

The problem I'm experiencing is that I can add multiple rivers into one already existing, but I cannot add additional streams from one that already exists. The editor just doesn't let me do that. So the only way to make a delta right now is to reverse the flow of the river, then I can connect the rivers, but that's functionally and aesthetically not really a good solution;/

Any ideas here?