Hi thanks for the suggestion.
This is something we'll keep an eye on, to see if other users are feeling the same. At present we feel that pressing B and 'not' going all the way back would be more frustrating on the whole for players who do want to go back (to the game) quickly after performing a certain operation (which would be more common). As you say we have the LB / RB to tab between. Its also why we've been careful also to say EXIT or CLOSE on (B), as opposed to BACK.
I think when players are used to it, using the LB / RB is very fast, say for example you want to make a cell, you need foundations, flooring, room type and objects. You can do all that with the tabs, and without needing to go in and out of the menus.
We 'could' add in a separate "Back one step" button but the UI would start to get a bit busy, plus finding a free button for that is a bit tricky.