I believe I've seen this done before, but I'm not actually sure how to do it myself. I have multiple InfoPath forms created for a list, and I wanted to see how to go about being able to access these different forms from the list item's Open Menu (the ellipsis that appears on a list item, in order to edit, view, etc). At the moment, I only have one content type (if that matters).
You can create Custom List Item Menu using SharePoint Designer.
Open the Site using the SharePoint Designer->Select the list where you would like to create the list action menu->Custom Action Button -> “List Item Menu” to create the custom list action item: