I’ll share something interesting for me but maybe obvious for others.
I’ve calculated that these mods are multiplicative not additive.
Meaning you get (100%+60%) x (100%+120%) = 1.6 x 2.2 = 3.52 multiplier which is 252% more damage
instead of 100% + 60% + 120% = 2.8 multiplier which is 180% more damage.
The formula for sheet trauma damage for a character wielding the sword and the shield is:
78 x FW% x (100% + sheet_trauma% + cunning_trauma%) x 3.52
78 is from 390 / 5 → 
dmg/s
[edit] I confirmed this by testing it on dummies.
That means Grim Tools incorrectly displays the following:
(should be 252%)
Which is consistent with the test I made for CT: Total Damage Stacking