Ok, sometimes needs just selecting opaque from only one layer.
Sometimes needs add opaque from another layer in to current selection.
Sometime needs subtraction opaque (but we may do it with first two and inversion).

I remind. It's the proposal to replace the current method of changing only one brush parameters — the brush size with "Shift + Drag LMB" — with the expansion of amount the available parameters. And only one additional gesture (vertical) for it.

Have opinion:

@scottpetrovic
I know some people who have a simple tablet and stylus no works with side buttons. What will we do with it? :)

@gdquest : Yes, this is a little new UX in Krita currently. But not new UX globally, I mean. And yes, potentially it should replace a Shift+LMB staying a rapid. And if there is a choice between a pie or list, list is more usefull for Krita (in all my experience). And list is easier and clearer to configure.

@gdquest
Yes, it is exact same sliders and switchers what we have everywhere in Krita. But in one simple menu (fly-on-the-canvas) for fast access. And this table stored inside a brush preset.
}

On my opinion this is more usefull implement — https://phabricator.kde.org/M20#424

We have a hot-key (type:press&hold) for fast calling a menu with list of custom options. Control with gestures: up-down — select a field, left-right — change & apply value. With invisible cursor.

In 2.9.10 Animation Edition (beta) — https://www.dropbox.com/s/44rvc94e0ey5ugh/krita_movtool.mkv?dl=0

Move layer to group and suddenly...