The shortcuts are not configurable within the app. I guess you could make a custom shortcut outside that captures that keystroke and does nothing (using something like Keyboard Maestro?). If that’s possible you’d also need to ensure that shortcut is ‘loaded’ on the system before you open Tinderbox so the existing shortcut suppresses Tinderbox’s shortcut for that key combination.
Generally, selection/sizing/movement in the Map view is done with the trackpad/mouse. You can use the left-right arrow keys to cycle through the note’s objects in $OutlineOrder, though once you get to the first/last item there is no selection (i.e. you can’t use the arrow keys to go ‘back’ without first selecting an item).