Whoops - my fault, sorry I misunderstood you there! (And for taking so long to reply - that darn real life…can’t live without it!)
As far as I know the “right” / easiest way to change AuthID for a destination is just clicking the button as you describe. Note that you MIGHT need to deauthorize Duplicati first (which you’d do through the destination’s interface, so varies by destination) otherwise you might just get the same authorization repeated.
Of course it is possible to get auth IDs from elsewhere (like directly from the some destination GUIs) and just paste it into Duplicati, so that might be worth a try as well.
Oh - and thanks for the “new user perspective”. When working with something so closely it can be easy to gloss over things that seem obvious when they aren’t. While I can’t promise things will get better quickly, we strive to move in that direction.