Support › MB Custom Post Type › show in menu is undefined
when i try to use the php code the post type doesn't appear in the menu because instead of "true" I get undefined
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Please try to deactivate all plugins except Meta Box, MB extensions, and switch to the default theme of WordPress (Twenty TwentyOne). Then go to the tab Advanced > Option "Show in menu": Show as top-level menu and Update the post type again.
Let me know how it goes.