I noticed that Kris Verma had two custom columns in his TradeIdeas window here:

I appealed to members of my Discord chat for the custom code that creates them and “Stonaphile” came through. Thanks, Stonaphile!

This is for the fade from the pre-market high percentage:

([BelowHighPre]/([Price]+[BelowHighPre]))*100

And this is for the fade from the regular trading hours high percentage:

([BelowHigh]/([Price]+[BelowHigh]))*100

Let me know if you have any trouble implementing it…