You should be able to select a batch of thumbnails and from the Photo menu choose Edit In >> Photoshop Elements Editor
When all the images open go to the Enhance menu to create a pano.
For PSE it’s best to set up the External editing Prefs as 8 bit PSD as 16 bit editing is limited.
But you can now make Pano’s and HDR’s directly in Lightroom. See this quick video: