Responding to Chrome widgets

I'm trying to make a new StrokeIt app for the Lucidchart widget for Chrome (I'd call that a Chrome plugin). I use the Add Application Finder Tool, which registers the widget as "CLASS:Chrome_WidgetWin_1". Then I add the command Ctrl-Z for Lucidchart "undo". However, the associated gesture results in nothing.

It seems that the Chrome app overrides its widget. Am I doing something wrong? Is there a way around this? Is there a way to tailor a Strokeit app to a particular URL or domain?

Thank you for a great tool! It's worth keeping it going.

Mario