I absolutely love OBS 20 so far. Great new features and good anticipation for what people use the software for. What bothers me right now is the placement of the "default" button. From a UX standpoint it's not great. I've had many times where I accidently hit "Default" instead of "OK" and cleared all the changes I've made to a certain device.
My suggestion is to move the "default"-button away from the actionable buttons. The use-case for most users will be to make changes to the device they're trying to edit. So moving the "default" button away from the default use case will make it more an exception to the rule. The button is still there for people to use, but it's less of a cognitive load to decide which button to click (since there's 3 choices now).
Just my two cents.

My suggestion is to move the "default"-button away from the actionable buttons. The use-case for most users will be to make changes to the device they're trying to edit. So moving the "default" button away from the default use case will make it more an exception to the rule. The button is still there for people to use, but it's less of a cognitive load to decide which button to click (since there's 3 choices now).
Just my two cents.