"Are you saying you can change order after it's saved. And in Library module?"
Definitely not an 'Exported' rendered video of the slideshow, but, Yes-
In a Collection, that being a special Saved Slideshow Collection, you can custom order the images (before you play or finally export the video).
A 'Saved Slideshow Collection' is not only a list of your SS photos but it also stores all the design and layout you have used for that SS.
The Saved Slidshow Collection can be viewed in Grid view [G] (like any other standard collection) where you can sort the images in a Custom Order.
Return to the Slideshow module layout by-
a) [Ctrl+Alt+5] , or
b) [Double-click] on the Saved SS Collection, or
c) [Click] on the small arrow at the end of the SS Collection when you hover the cursor over the Collection name.
If you close Lr-Classic and later re-open LrC to return to the same Slideshow you must return to the slideshow by opening the Saved SS Collection (NOT from the top module menu!).
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