You are right. I was prepared to explain too the case of a customised set of colours, but found it would seem tricky.
Load default loads the standard settings of Windy and you loose your own settings.
A solution is to set the threshold with a different browser than the one you use currently, without logging in. But you can do it only with the Windy set of colours, not with yours. This is the reason why I made the example here above with standard colour set, not with mine.
Otherwise as you say, keep a copy of your code in Word or similar software. See [view code]. At the end, paste your own code to get back your colour scale without threshold and click [import].
(In any case when you make sophisticated colour settings, it’s better to save a copy of the code somewhere !)

As a conclusion, if you have 3 or 4 colour sets with threshold,

Paste their code in place of the current one.

Then restore the code of your usual settings without threshold in the same way.

You can do it with your usual browser, but never click Load default.