Is there a way to import a photo into another photo's develop history? After retouching a photo in Lr, I went on to make some final changes in Ps. However, after editing in Ps, I would like to still make some changes in Lr. Do I have to Import the post-Ps photo separately? Or is there some way, to import it and make it sort of a part of the original's developing process?
The closest approach I know of to do what you are asking is to edit the photo in LR then open it as a smart object in PS. Once in PS you can add layers and masks to alter the photo, but you can't change the original. But if you decide that there is something else you want to do in LR, you can go back and do more edits in LR and not lose the layer mods that you did in PS.
But in general, once you use PS to alter the underlying pixels in the file that came out of LR, there is no way to go back to the original LR edit and keep those altered pixels from PS intact. You would have to open the new file that came out of PS.
A lot depends on the type of edits that you are doing in each tool. If you can provide a more detailed workflow, there may be a specific solution to your specific need.
Assuming you have both LR and Photoshop installed. Right click the image thumbnail in Develop mode, then choose 'Edit in Photoshop'.
Photoshop will load with the image. When you quick Photoshop and return to Lightroom, you will see your edited Photoshop image, usually with a .psd. You can then edit this image in Lightroom as usual.