Setting

Change Editor Keymap to vim (or emacs) at Preferences -> UI -> Editor Keymap Reload Boostnote after saving with “Command + R”.

Custom Keymap

You can customize your keymaps.

If you want to set jj as Esc, Go to “View -> Toggle Developer Tools” from the menu and after setting the tab to Console, Run the following script in the developer console.

CodeMirror.Vim.map (‘jj’, ‘<Esc>’, ‘insert’)

Specification

:q to escape from Edit mode.

When editing a note, : q : qw :: wq : q! commands let you leave edit mode.

Reference