custom attribute with data type Timeline

Hi,

I tried to create a custom attribute with data type timeline in RTC 3. It worked well and created a custom attribute. But when i wanted to add it in Editor presentation its not showing this custom attribute in the list which appears when i click on "Add Presentation". However it works for other data types. Is there any limitation with data type "timeline" or is there any other way to make this timeline appear in editor presentation.
Please clarify.

Thanks,
Vijay