Just updated to 2.50 but haven't dived with it yet. However, as always I did a lot of sims.
I noticed that there is a third page in the Gaslist menu (after the Gas 6 programming page) where you can apparently activate or deactivate gases !
I had never noticed this before - but then I must confess I never went past the first page in Gaslist menu, when doing actual Trimix dives. I just switched gases

So ... is this new ? and does it work underwater ? In sims, you can do things like deactivating your oxygen while still at depth and see the decotime being re-evaluated after a few cycles.