2 options, none too fast.
First one is that since AC only stores a limited set of orientations if you create new ones instead of selecting the previous ones will disappear from the list.
The other is to do a "New and Reset" to create a new File and that will remove all orientations and then you can open the previous file. For this one if before doing the N+R you have the orientation set to the one you want to keep then when you open the file again this orientation should be there.
Eduardo Rolón AIA NCARB
AC27 US/INT -> AC08Macbook Pro M1 Max 64GB ram, OS X 10.XX latest
another Moderator