The solution is to move the original folder using LR. That would be fine except LR sometimes has problems when moving folders around (At Least in My Experience). I have asked it to move images to a different folder or folders to a different drive and In LR it looks like it has done it. But then when viewing the original folder where the images were they are still there. Looking for the original folder in the original drive location the folder is still there and not on the other drive letter. But LR thinks they have moved them and shows them as moved. This doesn't happen all the time, sometimes it actually does what I want and need it to do. But not always.
So I have come to the conclusion that if I want images moved from one folder to another or a folder moved from one drive letter to another I do it with the File Manager for my OS and then Reconnect the images or folders in LR.
Question is - Any suggestions for a workflow / plugins that would detect automatically
new locations for all under folders that are moved to my external drive ?
If they are all under a parent folder, you could move the parent folder and then reconnect the parent folder.
If you are not using some type of travelling setup where you go somewhere with just the computer and not the external drive:
You should also put the photos on the external drive when they come straight out of the camera, eliminating the need to make the move. There is really no advantage to put them on another disk first and move them later.
Thanks for both suggestions - I try to archive work on slower cheap large drives - but want the speed of SSDs from start .
it looks like I need to reconnect folders manually ( as doing it for now ) then ...
There is no noticeable speed benefit to putting your photos on an SSD. Put them on the slowest disk you have, you will not notice the difference.