Update
We do not have the capacity to do an impact analysis to measure the improvements we're making to the Toolbar/edit flow without cutting our analysis of Edit Cards or the VE as default A/B test. We will instead more finely instrument the "edit flow" so we can better understand how contributors move from "starting" to "finishing" their edit(s). We will implement this instrumentation after v1 and potentially v2 of the toolbar has been released. The work for this instrumentation now lives in this task: T229079

cc @Neil_P._Quinn_WMF @DLynch @iamjessklein