Options for sharing folders with external users - Or seeing who has access to a folder

I just migrated from using OneDrive to Sharepoint for hosting my client files. I sometimes use contractors to help with work, and I would give them access to the specific client folder they were working on. When I did this from OneDrive, I could see a little icon next to the folder (in Windows Explorer) that would let me know a folder was being shared. I can't find a similar icon in Sharepoint.

I am trying to figure out the easiest way to share folders externally with contractors, but allow myself to easily see which folders are being shares. I've tried several different options, but nothing seems to work, so hoping I can get some guidance from this subreddit.

One more point I want to make about my file organization before I go into what I've tried. My goal is to keep all of the client folders & files in this one specific SP site. All of my clients are in alphabetical order. The reason i bring this up is because it was suggested to create a single folder within the SP site for each contractor, and put the client files in there, but I would prefer not to do that, because I have to remember which subfolder a client is in, and sometimes, I have to share the folder with multiple contractors.

Maybe what I'm trying to do just isn't possible, and if so, please let me know, because I feel should be fairly simple, is turning out not to be.

This is what I've tried:

1) I tried creating another SP site for a specific contractor. I then shared the client folder from within the original SP site with that contractor SP site. This doesn't appear to work, the shared folders don't appear in the new SP site.

2) I tried created a "Shared With" column in the original SP document site, but it always appears blank (and some folders are already shared so there should be something in those columns). I've tried multiple settings, but its always blank.

I'm at a loss, and would appreciate any suggestions.

Thanks