Can't collapse folder tree

I am giving Mailspring a try because it (supposedly) supports unified Inboxes. I installed it and added one email account (a .live.com account) as a test. In the usual email client or web portal, clicking on the account’s name collapses (or expands) the folder tree. However, when I try to collapse the account tree into in Mailspring, it does not work. Nothing happens. Clicking the little dropdown arrow to the right of the account name brings up 3 choices, none of which is to collapse the tree. Seeking advice. Thank you.