Try this:
Get the 2 inventories into separate windows
Press and hold shift then drag every stack/item from one inventory window to the other (at least you'll get rid of the "how many do you want to move" request)
And for merchants:
pressing and holding enter and then "just" clicking on the items/stacks will be a bit faster (but you'll have to check which of shift+enter and enter was for resale respectively to merchant only AND be careful not to sell the wrong thing)
Get the 2 inventories into separate windows
Press and hold shift then drag every stack/item from one inventory window to the other (at least you'll get rid of the "how many do you want to move" request)
And for merchants:
pressing and holding enter and then "just" clicking on the items/stacks will be a bit faster (but you'll have to check which of shift+enter and enter was for resale respectively to merchant only AND be careful not to sell the wrong thing)
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