Thank you for using our services.
Actually, the permissions you're referring to are configured through a public control, calle ItemActionPermissionsList. Since permissions in this control are set by calling the Permissions service, the only way you can add additional logic to it would be by mapping the template of this control, adding your own control to the markup (for example a textbox) and in the code-behind execute your own logic. You can use the permissions API from our documentation:
I'm attaching the default template to this reply. To map it through Sitefinity go to Administration -> Settings -> Advanced -> Viewmap and create a new Viewmap instance wiht the following details:
Hope this helps!
All the best,
the Telerik team
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