this just triggers my entire spectrum of love for this text-to-diagram, but I always struggle with increasing difficulty managing content as the complexity grows.
I actually find this acts as a useful heuristic to bound the complexity of a diagram appropriately. For example if I'm making a diagram with Mermaid and find the code is becoming unwieldy, I take that as an indicator that I'm trying to stuff too much info into one diagram and I should split it into separate diagrams or redo it at a higher level of abstraction.
If you edit these manually - yes.
Usually these sort of tools are meant to generate output programmatically.
Otherwise dragn'drop could be more useful.