With the upcoming update, you’ll be able to add any menu item to the toolbar — including default items, extension-created menus, and submenus.
Release 1.27.3 · MarkEdit-app/MarkEdit

In addition to general bug fixes and the new MarkEdit.runService() function, you can now add any menu item to the toolbar using editor.customToolbarItems. See v1.27.0 notes for macOS Tahoe support,...

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