I have customized my quick_element.xml toolbar file to create icons that insert custom elements into my documents. This works great. I really need to extend this toolbar so that the icons insert an element with a specified attribute setting. This would save massive amounts of clicks (I know this is possible for keyboard shortcuts via extendscript). The documentation is sparse and the available syntax is not documented for the <ELEMENT> tag in tag-description.xml.
My Structure Tools plugin can set attribute values automatically upon element insertion, including dynamic values like dates, times, etc. It also has a much improved attribute editor. You can try it out for free: