Missing libraries?

So, if I double click a slide in lighttable, sure enough, it takes that slide to darkroom. However, it is my understanding that within lighttable, a single click highlights a slide and makes copy/paste history stack possible. instead, as soon as I remove the mouse cursor (it’s active when I hover the mouse), the slide is then inactive and items like “copy” are grayed out.
I’m not sure how to take a screenshot of a slide NOT being selected…but hope my verbiage clears this up.