I don’t think you save a button. After typing in a field you will have to indicate that you have finished entry for that field (otherwise how does Rhino know?). Lets say tabbing out is an indicator. As things stand (in Windows anyway) you don’t need to tab out of the last box you want to change because you can hit Enter. If you couldn’t do that you would have to tab out, so same number of keys.
If tabbing out causes an update to the drawing (and if you don’t have the final enter then it must do because Rhino can’t tell from that tab if there is another change to come) then every box you change is queueing up another drawing change. If you are working on large, complex or heavily multiple geometry, that is going to slow things down. Enter has the advantage that you can choose to combine all the transformations and apply them in one hit.
p.s. Although voice response would be good, “Add ten to X, wait for it, Y minus 3, wait for it, rotate around z by radian over two, wait for it, move 10 in the z direction, go Rhino!”