In the Brush/Modifier Palette there are two sliders — one called “MultiMesh Select” and one called “MultiM”.
Both have the same interface path “Brush:Modifiers:MultiMesh Select” but are different sliders with different value ranges.
Recording a Macro gives the exact same path for both as well, so it can’t just be the info that is wrong.
I am confused.
I think this is probably an oversight. As far as I can tell, the second slider always has a range of 0-3 and does nothing; it looks like an unused duplicate which was included by mistake. The first slider’s range will vary depending on which MultiMesh Insert brush is selected, and setting the slider to 5 (for example) will select the 6th brush variant.
If you want to be sure of setting the first slider in zscript, you can use the numerical ID, e.g. [ISet, 1080, 5]. (The numerical ID for interface items can be found by examining the Preferences>Utilities>View Window Id slider, or using the item path with [IGetID]. However, note that some items, especially in the Tool palette, do not return usable IDs.)