Recently I received these questions:

Do you know if it is possible to create / edit reactions with Visual Studio as the editor? Could you recommend a best practice to instantiate power copies programmatically?

My response:

Unfortunately, most knowledgeware functions must be written in the KW editor. As for Reactions, you have the option to select a language, and if you select Visual Basic, then you could theoretically edit your action in the Visual Basic Editor or Visual Studio (with VB5 settings), and then copy and paste it into the Reaction editor.  But at that point, you might as well just use the standard out-of-the-box editor.   (FYI, not all functions are exposed in the VB Reaction editor that is available in the main VBA editor, e.g. some error checking, etc.)
This page shows how to instantiate powercopies via VBA: