How to add custom dropdown in campaign and message template

I have made custom entity (dynamic data) of events, Now i want to add this entity's data set (for example, Event Name) in the drop down at campaign and message template as place holder like preloaded drop down of "Insert dynamic data in the text".

When user selects any event from the drop-down, a link of the event appear in the text editor, please refer attached image.

Hello Ashfaq,

There is feature request logged in the Public Issues Tracking system. You could vote for the possibility to have custom predefined fields in dynamic data list on that link. When the release is planned the PITS issues and their votes have huge impact about the features that will be included.

Regards,
Svetoslav Manchev
Telerik