Opacity level for masks

Thanks for that background. Yes, hiding in plain sight. The interface is non-intutive, but I'll take it. So much better than fading the individual adjustments to get a milder version of my presets. Thanks again for so swiftly teaching me that tip.

Apparently that one has hidden in plain site for years. I learned that it has existed for hears when I requested that the slider be part of the mask adjustment panel instead of requiring the above click on the triangle, Other members responded as such in my Idea I posted requesting it be incorporated as a part of the mask adjustment panel, instead of behind the panel

https://community.adobe.com/t5/lightroom-classic-ideas/p-masking-various-masks-amount-slider-on-panel/idi-p/12485816

I have not used it. I just stumbled upon it. But perhaps this link:

https://jkost.com/blog/2018/12/using-the-amount-slider-with-creative-profiles-in-lightroom-and-camera-raw.html

or

https://www.youtube.com/watch?v=JiO8mlIQDwQ

(a bit old)

P.S. That triangle is causing accidental problems for many members. typically they find that the entire photo gets edited after applying a mask, turns out they clicked on that triangle, then did not notice they were making adjustments in the Basic Panel. 

Wow, thanks for that tip, @GoldingD . I had not idea it was there. I've wanted to use that functionality for years. I googled a lot and never found it. Is there an Adobe page that documents it? Does 0 mean full strength mask and positive numbers some multiplier, while negative numbers a fraction of 100%? It's strange that the numbers go from -4 to + 4.