How do I work on two things at once?

Two different repositories

File ▸ New Window (⌘N) opens another window, and File ▸ New Tab (⌘T) puts it in a tab of the one you have. Each holds its own repository and each refreshes itself independently.

Two branches of the same repository

One window holds one repository at one position, so switching between two branches means moving your working copy back and forth.

The usual answer is a stash: put the current change aside with a message, switch, do the other thing, switch back, restore. Innesta will also auto-stash when a switch would otherwise be refused, and put that stash back when you switch back — the same loop, with nothing to remember.

If you find yourself doing this several times a day, a git worktree gives the same repository a second working directory on a second branch, and Innesta will open that directory like any other:

git worktree add ../kettle-hotfix hotfix/1.4.4