I have read the below guide from moving items from one library to another and it is hilariously time consuming and complicated for such a basic feature that has existed in all sorts of applications since computers had transistors.
So nobody there at all is saying just create a new Library and link it the same the parent folder in the share.
Assuming that previously there were multiple sub-folders created for multiple libraries but now the user wants everything in just one library linked to the parent folder, or vice versa where originally it was linked to a large Library but then individual libraries were now needed to be linked to sub-folders.
So, what reason is there for not having the same file(s) with the same file path in different libraries?
It depends on your library structure. You can have the same paths in multiple libraries. but you will probably end up duplicating more than the single file you want to mirror (unless you want a set of files to overlap)
FYI tried and the Plex Manager Server did not like it at all, it couldn’t make heads or tails of what it was scanning for the new library. The first TV programme was stuck in a loop (Ted Lasso) and eventually was trying to match more than 10,000 episodes to that series. The number matched the total episodes for all shows I have yet it thought every file for was for Ted Lasso. Thankfully the original libraries remained intact but I suspect they too would have had issues had the scanner been allowed to progress to them.