In 1.15 Mojang added a new Accessibility Setting where you can set the shift key to toggle sneaking instead of having to hold it down. This is good to reduce RSI/carpal tunnel when building things.

This interacts poorly with Quark's smart crouching features.

Easy repro:

1. Enable toggle-on-press for sneaking in Accessibility settings
2. Start sneaking (press shift once)
3. Open chat -> you unsneak
4. Close chat -> you resneak

Expectation: You stay sneaking

Are you sure this is a quark thing? Opening chat seems to unsneak me even if I have the quark sneaking code disabled.