I don't know what people think but maybe the change from Places←→Directory tree could be put in the 'View' menu or in the preferences so as to leave more space in the side panel?
I think the old pcmanfm had a button for that, right?

For me it isn't really needed to be quick to access that but for some people may be, I don't know. But trying to leave as much space as possible in the side pane is good.