".widget-button", ".button-element", "widget-button-text" etc. are included in various tutorials for thingworx yet there is zero documentation on these values. I'm surprised that there is no basic documentation on these keywords. I feel like it's not too much to ask for to display what selectors are available to developers on the widget description pages.
Referencing post: https://community.ptc.com/t5/ThingWorx-Developers/Thingworx-CSS-Selectors/m-p/636294#M40612