For now, all you can do is zoom in and out since the selection size is a fixed number of pixels.
I tried some automatic size changing but that turned out to be a nuisance. Can you describe your use case a bit more? Maybe it needs an old fashioned dropdown menu to specify the size.
I want to select lateral faces of some Shell elements. If I zoom out to see all the component, when I try to select the faces some front faces are also selected.
You mean edge faces? That's often easier by selecting nodes first then changing to Select faces mode. At least for straight edges. Paint selection is still not much use for those unfortunately.
Comments
I tried some automatic size changing but that turned out to be a nuisance. Can you describe your use case a bit more? Maybe it needs an old fashioned dropdown menu to specify the size.
If I zoom out to see all the component, when I try to select the faces some front faces are also selected.