Is there a keyboard shortcut for the “Show Fullscreen” command? I don’t mean the “Full Screen” command which only shows the contents of the thumbnail window. I mean the equivalent to that little right pointing triangle overlay button that I have “Show fullscreen overlay button” turned on for, that fills the entire screen with the image.
I’ve been faking what I want by setting the slide show to a very long interval and then starting a slideshow with the “All” command.
Do you have a chance to make a screenshot with that triangle? I don’t think I have ever seen it
You get it by turning on:
Settings > Configure – digiKam > Views > (TAB) Icons > Show fullscreen overlay button
I found it!!
Got to Settings → Configure Keyboard Shortcuts
There, search for “OpenGL Image Viewer”. And assign a shortcut for it.
It is really hidden to find it, the name is not clear at all.
Edit: I just noticed, that is not exactly the same as the “Show Fullscreen” command. The “Show Fullscreen” command actually calls the Slideshow, with the current selected image being the starting point. The OpenGL Image Viewer looks similar at first, but it does not have an option to play the images as a slide show, display the rating, etc. It will just show the plain image with no distractions. This is nice, but also possible with the Slideshow, I wish there was a shortcut to call the Slideshow directly from the current image.
Thank you. But like you mentioned it is SOooo close. It’s very similar, but since it won’t show info like the image name, I’m not sure I want to use it.
OK, we are getting closer 
In the settings of the slideshow (F2), you can select “Start with current image”. That way, when I call “Slideshow - Play All” (F9), it will start playing with the selected image.
The only problem is, that by default, it will start playing the Slideshow automatically. So there is an option missing, something like to uncheck “Play on default.”
However, as you mentioned, you can either select a longer interval time by default. Or, you can press the “Space” key right after opening the slideshow. That will pause it.