So you're saying I can't do Shift 1/Shift 2/Shift 3/Shift 4 and Ctrl 1/Ctrl 2/Ctrl 3/ Ctrl 4 using ABXY and two triggers?
you can do that using ABXY and 1 trigger.
Make A = ctrl + 1 (there is a button in the steam config called "multi-button" that lets you hit button combinations)
B = ctrl + 2
X = ctrl + 3
Y = ctrl + 4
then make, say, LB the mode shifting button, when you press the mode shifting button, you are basically presented with an entirely new set of ABXY buttons you can set
so you'd set A = shift + 1
B = shift + 2
X = shift + 3
Y = shift + 4
but, what might be perhaps better, is to make
A = 1
B = 2
X = 3
Y = 4
then make one trigger be ctrl, and another trigger be shift.
ALTERNATIVELY, the left analog stick has one extra feature not on the 4 face buttons - a second "outer ring" shift, where, once you pass a threshold, a certain key is automatically hit.
so you could make a little tilt in the cardinal directions be:
up = 1
down = 2
left = 3
right = 4
then, the outer ring modifier be shift, so if you hit the stick all the way, you get
up = 1 + shift
down = 2 + shift
left = 3 + shift
right = 4 + shift
then use mode shifting to present yourself with yet another blank analog stick, which also has it's own outer ring binding. In this way, you can turn the analog stick into 16 different inputs... but it's not optimal.