It's been a long time since I last used Lightroom, so I certainly am rusty. Please note the attached screenshot. I am trying to do a focus stack, and to do this first the images are processed in LR, then, I believe, the next step is to highly > r-click > Edit In > Layers in PS. As you can see from ythe screenshot, this option does not appear immediately available. Please advise.
Also, how come there are no tabs for Library, Dervelop, etc.?
You have selected multiple images. Lightroom does not support sending more than one image at a time to Photoshop. As you are asking about the Library and Develop modules, it seems you have installed the wrong version of Lightroom. What you need is Lightroom Classic, not Lightroom.