AS Slyder:
I suspect it's no longer available because someone in MS application development is trying to make a name for him or herself by replacing old, albeit proven, features with new, by definition unproven, 'features.'
I did find a decidedly less effective way to display a slideshow in Windows 11:
- Right-click on the folder containing the slideshow images.
- Click on 'Select more options ...'
- Click on 'Add to Windows Media Player playlist.'
It may take awhile for WMP to build a playlist, but it eventually displays the slideshow with precious few adjustments available.
Tom