this works, but in order to see both sets of edits there are some options that apply. Whenever a conflict is found (images in the two catalogs both have the same source file in common) you can choose which version is to "win" (the incumbent or the incoming), or else you can opt to keep the present version AND the incoming one too (using virtual copy).
There will then be a cleanup process of keeping / discarding versions. Perhaps (considering photos which you know to occur in both catalogs) it may be worth pre-removing - without deleting from disk, of course - all unedired photos from one of the catalogs. Then at least those will not need any subsequent cleanup.
As always, good idea to start with up-to-date backups of everything.