Rich text editing has been an ask of Dynamics 365 for a long time. Now, such controls have appeared in the Unified Interface but only in a limited way.
In my moderately brief review, I see the position as this:
- Rich text controls are available in the Unified Interface for Dynamics 365 Online version 9.0
- They are only available for the Content field in Knowledge Articles and the Description field in Emails
As far as I can see it is not possible to have the interface show rich text controls for any other field.
There are many articles that describe how to add CKEditor to tinyMCE to Dynamics using JavaScript but of the several that I examined, they all use unsupported techniques that reference the document object model rather than the provided object model (see https://docs.microsoft.com/en-us/dynamics365/customer-engagement/developer/clientapi/client-scripting-best-practices for more details).