Currently, many-to-many relationships (i.e. apply to a job, join a group, etc.) can be accomplished only with a checkbox UX control (see For example, two-sided products/marketplaces need a many-to-many relationship where one side is applying to the other side. In the current interface, I can add an item as a favorite, save it to a list, etc. but I can't apply/submit myself to that thing (a project, a job opening, etc.) apart from using a checkbox control. A button is a much more standard and expected UX control for this function (i.e. a button labeled "Apply to this job/group/etc.").