When the 740 was current, there was only the fixed array user memory for Registration saving (ie you couldn't add more); they didn't really have to ask where to save; there was only 1 user memory. Now you can have user, USB1, USB2, etc so yes, it's going to take an extra button press at least. And since there's no file undo, they also need to make sure you're not overwriting an important file. Fred is 100% correct; why on earth are you changing registrations *while* performing? The whole point is to have all your settings pre-saved and then just call them up as needed.
Also, if you recall, you had to save all the registrations banks in one go onto a floppy drive; and if you wanted to load a song or style you couldn't read it from the disk, you had to copy the file into the one of a handful of user memory slots for songs (I think styles worked the same way; it's been a while since I've had a 640/740 in front of me). *That* was inconvenient! I was very glad when they changed the OS to the (still in use) non-touchscreen file i/o where you could load from your usb/floppy without having to erase the user memory song/style first!