I don’t know when it was dropped but I find the current method of just clicking on the plugin name rather hit and miss – especially with plugins that take a while to load like NI Kore it often looks like they are not going to open so I think I have not clicked right and do it again which makes them close as soon as they have opened. I prefer a clear cut on/off button like the old edit button.
When I start a redesign of the track headers (hopefully within a month or two), I’ll make room for plugin editor buttons. The plan is to get rid of the overcrowded UI controls in the track headers, and instead present them on a larger popup panel.