I understood your question. But does this make sense in the context of Joplin compared to a mind map?
Say for current note A you want to make a link to new to be created note B. Hence there is a link reference inside note content A needed. Where exactly in A should the link be inserted?
If you are asking to append this new link to the end of A - no, that's not possible atm.
The idea itself is interesting - some kind of context menu with additional actions, when right clicking one of the notes in the graph.
