Can your editor's auto-complete and markup help be extended for other "dictionaries"?

Just got back into web dev after several year hiatus. Boy have things changed! Anyway, I still enjoy using your editor but typically start with frameworks like bootstrap or skeljs or lately my own customized version of one of those. It would be great if the editor would recognize framework-specific elements they way it does HTML or CSS elements.

Is it possible for me to extend the editor using the markup files? Any suggestions on how to make that happen?

Maybe this.
Try clicking on "Tools" then "Preferences" then the "Customization" tab.
Now click on "Open Markup Library".

Thank you. I looked at that and it certainly helps where additional tags are introduced like "data-content" or what have you.

The thing is most of the interesting bits are tied to class names like ".button" ".button.small" "icon.icon-ok-sign" etc. I didn't see any way to predefine any class names -- which makes sense since they are intended to be user-defined. However in the framework world the class name can have a predefined meaning so would be helpful to have some auto-assistance in typing them in rather than flipping back to the documentation constantly.

I did notice that the editor does pop up a list of class names when I start to type in the class attribute. I couldn't see any way to pre-populate that though. Any suggestions?

That list will dynamically be generated from any style sheets you have linked in the page.