Not sure if the X-T3 differs significantly from the X-E3 but you can't add anything from the user settings menu to the my menu for quick access nor can it be added to the Q menu.
I'm used to lenses with no image stabilising and every time I've used lenses that have VR/IS/OIS, I have found that I frequently get blur that is actually caused by the stabiliser. The ideal option seems to be turn IS off if the shutter speeds are high enough that it isn't needed and if using it, always wait a moment for the stabiliser to "settle" before taking.
Some more with the 50-140mm
Chains by
Kyle, on Flickr
KMW02270 by
Kyle, on Flickr