Doors – How to add door trim where there isn’t enough room

Instead of changing the size of the opening, use a pair of 24" doors in the "bypass door" configuration. They'll overlap 4" when closed and you'll have a 20" opening when they're open.

If you want to increase the 20" opening, you can cut the doors to make them narrower and this will still be less work than changing the size of the doorway. Even garbage MDF doors can be narrowed almost an inch on each side, especially if you're not attaching hinges or real doorknobs.

Cut out the plate at the wall. let the drywall run up to the window and add a minor piece of wood, something like lattice to cover the difference at the edge of the window to the new ceiling extension. It may take 2 pieces to form a new corner at the window, but I think the corner would be better at the window rather than at the wall face.