The idea is that the “auto” blend/composite/etc defaults to the technically correct option, either linear or perceptual depending. So as a user, you aren’t expected to have to keep changing these except on a layer by layer basis. So yes, having to reset each and every layer every time you change the layer blend mode is a hassle.
The hassle is made worse because the word “auto” doesn’t tell the user which option is being used, which is highly annoying. I opened a bug report on this issue awhile back. Please feel free to add a comment if this bug report addresses the situation you are describing:
Replace “Auto” in the Blend space and Composite space dialogs with something more informative - Replace "Auto" in the Blend space and Composite space dialogs with something more informative (#1120) · Issues · GNOME / GIMP · GitLab
In your particular use case, I suspect the main reason you are resorting to constantly changing the blend and composite modes is as a workaround to the truly awful posterization you are getting as you try to softly shade an image. In other words, if the 8-bit posterized brush stroke issue were fixed, it’s possible that you’d quickly adapt to shading using linear instead of perceptual RGB. Leastways I do a lot of shading and I always use very low opacity linear RGB multiply for this task. But on the other hand, maybe your style actually requires perceptual RGB for this task.
There was a time when the “default/legacy” switch in the layer dialog could easily have been converted to a “linear/perceptual” switch on a layer by layer basis, but that particular suggested code change never got incorporated - instead we have the “right-click on layer” to accomplish the same thing. But I think more goes on with “default/legacy” than just the RGB encoding, which might be why there are two ways to get from linear to perceptual.
If you think it’s worthwhile, you might want to open a bug report requesting a way to set a given layer to a specified composite space and have that stick throughout the layer’s life and regardless of changes in the layer’s blend mode.
Changing topics, I suspect that this “8-bit posterization” bug you’ve uncovered is why I keep piling on texture/fade/small color changes/noise/etc in the brush dynamics that I’ve put together, in an effort to mask abrupt tonal changes that I never actually thought of as “oh, that’s at least partly 8-bit posterization”.
Not sure exactly what you are asking - are you receiving notifications when someone makes a post to the bug? If not, this can be controlled through your gitlab GNOME account.
If no one has any patches or comments, then nothing will be posted. Sometimes a long time goes by before any given bug is worked on. There are only a few devs and a lot of bug reports, and the main thing right now that most of the devs are working on is converting from GTK+2 to GTK+3.