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.
Clicking the account name doesn’t do anything because that dropdown at the top is an account switcher (your account(s), Add Account…, Manage Accounts…), not a tree toggle. The collapse control lives on the folder section headings further down instead: hover over a heading and a small Hide link appears at its right edge; click it and the section folds up (it turns into Show). Nested folders also have their own disclosure arrows.
One thing about your test setup: those headings are only collapsible when there’s more than one account connected. With a single account the sidebar is just “Inbox, Sent, …, Folders” with nothing to switch between, so the Hide link isn’t offered. Add your second account and you’ll see a heading per account, each with its own Hide/Show, plus the unified All Accounts block at the top, which is probably the reason you were looking at Mailspring in the first place.