I apparently do not understand something very basic. I have Lightroom (not cc) and Photoshop 2020 (again not CC). Both latest versions. In Lightroom I simply right click on a photo to "Edit in Photoshop". Works perfectly. Now... HOW DO I GET IT BACK INTO Ligthroom??? I am using the MAC version. Any help would be GREATLY appreciated. Driving me carazy!!!
Lightroom desktop does not work based on a catalog system and similar Lightroom Classic> Photoshop> Lightroom Classic round trip for editing and saving images is not possible.
You would have to save the image from Photoshop and reimport it in Lightroom desktop.
However, if you use Lightroom Classic you can get both the apps (Lightroom Classic and desktop) to get images back into the application after they are edited in Photoshop. This is because you can set Lightroom Classic to sync a collection of images to sync to the entire ecosystem which also includes Lightroom desktop.
I don't think that the advice about adding Lightroom Clasic to the mix or having to manually import the image is correct. Lightroom desktop and Photoshop can work together perfectly well without Lightroom Classic, and the photo should automatically come back into Lightroom. It may take a bit of time, because it needs to be uploaded to the cloud. One thing you have to make sure is that you do not use 'Save as' and do not rename the photo. Just hit 'Save', switch back to Lightroom and after a short while (depending on your internet speed) you will see 'Importing' in the upper left corner and your edited image will appear, stacked with the original. I just tried one to check and it worked as expected.