I forgot how I did it and help pages doesn't help really . Both Chat and Gemini know nothing . The whole random system looks like a bug maybe. But I am sure I did it before. it was in brush>modifiers as far as I remember .
Yet "Variation" and "variation select" slider in 3 position do nothing. Still same mesh inserted.
Hope somebody still use this last permanent version from free updates era.
I recall I did random meshes along a curve too , not just 3 parts. but now it doesn't work for me to. Would be appreciated for a help. Looks like it all works differently in current zbrush version and I can't find proper explanation anymore for 2022.0.8