Currently, Glyphs uses weight, width, custom, custom 1–3 as axis names, which inherits the structure from the earlier implementation but no longer makes sense since the support of axes custom parameter. I found it quite awkward while I was updating the Instance Slider script. Weight axis is just the name for the first axis, and if you put Weight as secondary axis, that’s internally width. Why don’t we introduce new axis names and deprecate the old ones in the future?
Also, unrelated minor issue: the Macro Window has tabs, but the tab names are not kept straight. You can end up with a lot of “Macro 7” tabs for example, depending on how you close tabs.