OSX Photos "keep folder organization" on 2nd import issues

I have about 100GB+ worth of photos neatly tagged and organized in folders by year/event etc. Lets say the top level Dir is called "MyPhotosDir". I start with a completely empty Photos app, import MyPhotosDir and check the "keep folder organization" during import and life is good.

Assume a month later, I added some photos to MyPhotosDir. I created some new folders corresponding to the past few months. I also found some photos for older years/months and added them to already existing photos folders. I then reimport "MyPhotosDir" and the new photos DO get added. But in Photos, if I look at the left side, there are now 2 instances of "MyPhotosFolder". The 1st one lists all directories/folders, the 2nd one lists just the ones that changed between the 1st import & 2nd import.

My goal is to keep syncing "MyPhotosFolder" into Photos, keep the folder organization, but only have one instance of "MyPhotosFolder". How do I do this?

I do NOT want to delete everything from Photos and start all over again! That looses all the face detection etc that has already happened.

Please help!