The functions to 'sell everything' and 'sell everything but 1 of each item' are not only near-useless (I cannot ever imagine a situation when I would want to sell everything or everything but 1 item each from a base, and I have never encountered such need in 30 years of playing XCOM)
I use these buttons after almost every mission.
The first 10-20% of the game, I use the "sell all but one" button... to easily sell everything for money but keep one of each for research/interrogation.
The remaining 80-90% of the game, I use the "sell all" button to sell all the junk (even more in mods than in vanilla), and just undo a few items I want to keep. It's much easier and quicker to select a few items I want to keep than always select all the items I want to sell.
PS: and yes, I know "auto-sell" feature exists, but I simply cannot use that... it's so wonky, I simply cannot trust it and/or use it effectively... I've burned myself too many times overselling or underselling (when the game thought it knows better than I)
That way it is easy to accidentally sell everything you have on your base by the means of a slight finger slip, meaning the need to replay two missions on average (because that's the usual amount of time before you notice what happened), which is both a major distaste and a lot of real life time wasted.
You can easily deactivate both shortcuts in the Options > Controls.
Just right-click to deactivate.
They will never bother you again.