Recently I started using the pure mode in my hybrid xc90 T8 Twin engine, and I noticed that the car always switches back to hybrid. Now, doing that at every start (i.e. getting in the car and switching it on) is somewhat annoying, but that it also switches back to hybrid when I change from driving backwards to forward is really annoying. Is there any 'secret sauce' to make the pure mode more sticky?

 

I haven't found a way to keep it stuck on pure mode.

However, after doing a fair bit of driving and testing, I found that just leaving it in the Hybrid mode is pretty much all you need to do.
The Hybrid mode will use battery only until the battery is depleted or you really press down on the accelerator for fast acceleration.

For me my daily driving is Hybrid mode in B and the single pedal driving is pretty nice and I get about 5 miles more than the listed all electric range.
(2022 T8 Extended Range).