When I edit a K2 item on the front end, it creates a lightbox popup.

However, if I create a menu item of type "Item edit form" and click on the link, it opens the item creation form in a new window or tab, rather than as a lightbox popup.

Could someone please let me know if this is working as designed, or is there a problem with my site?

Hi. Unfortunately, when you create a menu link K2 has no control over it. If you want to make a menu link open in a modal you need to implement it on your own with custom javascript code. Alternatively you can use the K2 user module to provide you the modal link.

I see, makes sense. Thanks for the explanation.

You are welcome.