installing sliding shower door when width is larger than tub
Make a 2” return on each end or 4” one end to support the sliding units which takes up the extra space.

Now you have added the picture I would go for the 4” - designed to match the shelf or just completely box-in that end... but that shelf area could be useful....

Some shower screens don’t go the full length of the bath anyway - I fitted one that is 2/3 of the bath length which works fine for the shower.