VERIFIED SOLUTION i

How to use multiple browser in EngageOne

Product Feature: Browser Management
 
"Cross Browser Support" was introduced in 4.4 which is specifically named as a new feature. Please check the Designer to make sure that the attribute option is selected as needed. (then do the template publish for that template to work in other browsers as documented)The information is in the Designer release notes on page 14:

Cross browser support
Designer 6.6 adds cross browser support for publications containing interactive data intended for EngageOne. The new Cross Browser Support option is available as a publication attribute. When selected, the final customer communication can be created in any supported browser without the need to download and install the ActiveX version of the Interactive editor.

More information on this topic is documented in the Designer User's guide on page 328. It's not *full* support, but it's an alternative and it should cover a lot of basic use.
UPDATED:  June 14, 2017