​@Leonid You'll need to either move the frames out of the Slides container, or duplicate all of the content (minus the Slides container) and then delete what you don't need. 

I'm on my phone right now, so I can't confirm this, but you should be able to:

1. Click-and-drag around the entire Slides container, which should select everything.

2. Using the filter in the context menu, filter to only the Frames

3. And the clock and drag the frames out. 

If that goes bonkers, undo with a Ctrl/Cmd + Z and then as alternate to step #3, try duplicating the frames instead of moving them (Ctrl/Cmd + D is a shortcut).

Another option is to use the Precise select which is activated by long-pressing the left mouse button and selecting everything inside of the Slides container (without, of course, selecting the Slides container itself). Then drag everything out.

Try the show as board toggle