best way to view a document you have already watched in the near past is to launch okular and to find its name in recent history.
Should be a prominent feature (spanned in as many apps as possible) to show recently used files in main window on launch, as Dragon Player does.
In this case should be important to add tab functionality to open new docs (anyway a feature that is actually missing).
Note this is the approach that also Gnome devs find appropriate - alongside with launcher quicklists.

Reproducible: Always