the problem is that in the viewport the reduced bones stop responding normally to commands, it is impossible to select with the mouse, you have to constantly fight, click to hit the bone, this is pain
I don't understand this because bone scale doesn't affect selection with the mouse. It affects 1) the bone visuals, 2) the viewport max zoom, 3) the space around region attachments when multiple image files are dragged into the viewport at once, and 4) the padding around bones when bones are rendered for image/video exports. It doesn't affect anything else.
It is also very embarrassing that normal selection works only on standard bones, if you change the view (icon) of a bone (for example: a star or a diamond), then the selection of the bone works only in its very center.
A zero length bone and a bone that has an alternate icon behave exactly the same for mouse selection. The size of the icon is not used at all, regardless of bone scale.
I can accurately select bones that have a length at any size, even a ridiculously micro size:
Loading Image
The bone that will be selected when you click turns white when hovered, as you can see in that image.
Zero length bones (including those with alternate icons, which behave the same) at this zoom don't scale down as small with the bone scale I'm using (bone scale 65 and bone lengths 1.3):
Loading Image
One way to fix this by using a lower bone scale:
Loading Image
We put extra effort into making zero bone scale work well and I actually really like having the bones drawn as a single line. It's less clutter and again mouse selection is unchanged. In 4.0 bone rendering is much improved, no flickering or jagged bones even when they are thin.
The same with icons:
Loading Image
However, I think it's not reasonable to zoom way out and then complain the bones can't be selected. If you are zoomed out so far there is very little space between bones, of course that will happen. 🙂
The bone scale is primarily to control the size of the zero length/icon bones at a reasonable zoom level that you will use for most of your editing. To set it, zoom to the level you will use to edit the skeleton, open the settings, move the settings window so you can see the skeleton, and adjust the bone scale until the icons are a good size.
When you are using an interface scale of 200, I found an issue with bone scale. The zero length bones using the default icon were too large! We've fixed this in 4.0.24.
Storing bone scale per skeleton is an interesting idea. I suppose a project could have skeletons at very different sizes, eg a giant and a butterfly. We'll consider making that change in the future!
