Non "requested" mask settings defaulting

There is a time window after opting to start a new mask, but before beginning to make the (e.g. painted) selection for that - where moving adjustment sliders gets remembered as user customised default adjustmenfs for not only this mask but also for future ones. Until you change those defaults to something else. The Auto Reset option is provided as a convenient way to disregard any previously changed defaults.

So: one can deliberately create a non-zeroed starting point for masks, but making use of that would require unchecking Auto Reset. As a downside of that (older) method: user-set default adjustments happen not just for that one kind of mask, but for all kinds of mask.

The option was since been added of saving out a (meaningfully named, preferably) mask into a develop preset. Thus we can then retrieve into our different image with one click a copy of that desired kind of mask, pre-loaded with those same adjustments (which may be zero or non-zero). Say: there is a lightening oval that we routinely use for certain kinds of photo. Or: a contrast boost for ‘Subject’ is common in our approach.

This we can then further adjust within the particular image: for its coverage (by all the various means available), and also tweaking its adjustments. But we’ve had a standardised starting point: and IMO more conveniently, than by first making a fresh zeroed mask and then recalling a chosen local-adjustment-settings preset into that.

​@Jim 185 

In you screenshot you do not have a mask selected so you can not reset it.  

To reset mask adjustments in Lightroom Classic, you can double-click the word "Effect" at the top of the masking panel to zero all sliders. To prevent settings from carrying over, check the "Reset Sliders Automatically" box within the mask settings panel

Sorry the preset is set to CUSTOM, not “default” as per the screen grab