Installed MSFS on drive D and it worked fine but it also installed parts of it including another community folder on drive C. How can I just get to one Community folder ?

I have the same as yours Paul. But there is only one true Community folder on my E drive, the one on the C drive only has links. You will also find a number of other MSFS stuff on your C drive in the "Microsoft packages".

As I am using Add-on Linker, all my addons are linked actually to both "Community" folder but the Add-on Linker only knows the one on the E drive. To verify what I am saying, go to your UserCfg.opt folder (located in your MSFS directory, open it and scroll to the very bottom of it, the last line will show where your MSFS installed packages are located, on mine it shows the E drive.

I moved (cut and pasted), not copied and pasted, Community and Official and from the default location to a new location. I have had only one Community and one Official drive anywhere ever since. Both in the new location. But I kept the new non default location on C instead of a new drive. In fact I only have one drive in the computer.

I keep another drive in the cloud using pCloud for any storage of stuff I can't afford to lose. As long as no other nation declares war on Switzerland and bombs both locations where pCloud has its main and back up servers, those files are really safe. pCloud is not a rental, you only pay once for lifetime storage.