Improve behavior of adding a communications data source variable in Design

[mfaith]

If you are currently using manual variables in your communications cog, you have already mapped the data sources in Design. If you add a new manual variable in Communications Admin > Data Source Setup, when you go back to your Communications cog in Design Studio, your new manual variable is not visible.  The only way to get it to show, is to uncheck and recheck the ManualVariable checkbox listed in the Data Sources drop-down list of the Configuration tab in Design Studio.  This more or less "refreshes" the data sources and you new manual variable is visible to be mapped.  The issue is that by unchecking and re-checking that ManualVariable checkbox, is it that it wipes out any previous mapping you've done to other manual variables and those have to be remapped.   See attachment