This has been a problem for a few years now and Im starting to go mad since its still an issue.
The problem seems to happen when you have a node editor or hypershade open. Then you hit "w" "e" or "r" to go to one of the transform tools. You then go to grab the UI tool in the viewport and Maya pops up an unwanted hotbox. You end up down several sub-selections in the hotbox before you realise it, and have to carefully back out so you dont turn something on by accident.
Then you have to select a different transform tool to "reset" whatever is going on in Mayas head, then go back to the tool you wanted before it will work. Its been driving me crazy for years.
This doesnt seem to be an issue if you never have the node editor / hypershade open, but I like to work with node editor docked above my main perspective view. Im always going back and forth and to have to close and reopen all day long would be just as infuriating as the bug.
go to windows > settings/preferences > hotkey editor
next to "search by: " change "Application Command" to "Hotkey"
left click where it says "Press key" in the search bar and press the w key
find where the w key is mapped to the move popup, click on it and click the x to remove the w hotkey from that option. i don't know what it is called because i already deleted it. this will delete the annoying hotbox.
you now need to set the w key to enable the move tool only.
change "Hotkey" back to "Application Command"
at the top, next to "Edit Hotkeys For:" change it to "Menu Items"
twirl down to Menu Items > Modify > Transformation Tools > Move Tool
click on "MoveTool" and enter w into the box
at the bottom click the "save" button.
do the same for rotate and scale.
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