When you set the multibrush tool to translate you can paint with multiple brushes at once. The radius slider now determines the size of your multi brush i.e it is the area in which the other brushes can appear. It would help me - and I guess other artists too - when the cursor shows the radius as a circle instead of the brush outline with it’s original size when the multibrush is set to translate. It would make it much easier to aim your strokes. Currently the cursor outlines shows the size of the brush preset, which can be much smaller and this makes it a bit of a guess work to place your strokes precisely. Maybe even both is Possible, like showing the brush outline and the radius around it where it is going to have an effect.
This is how I’d expect the cursor to look like when multibrush ist set to translate.