I am using SmartWord4TFS Update 2 Version 10.0.6.2 and TFS 2012 and Word 2016.
When creating Work Item templates through Smart Panel and Create Small Parts, I note that the AreaPath for Requirements
cannot be set nor with DropDownList nor with ComboCtrl, nor inserting its value manually.
Please note that this does not happen with the Wizard method, as available AreaPath values are correctly selectable..
A workaround is to left the AreaPath unassigned, publish the Work Item, using the edit WorkItem Option in the error window,
selecting it in TFS, refreshing the template, and only then Create the Small Part.
Then through Authoring-Insert Small Part other Work Item can be generated, with the same parameters values as the first Work Item,
if so specified in Create Small Part,
I hope this helps.