If I'm reading this right, the simple button option results in a button that is labelled "Add."  How about we change that so it uses the user-defined label text as well, ie:  "Add Participant."

The catch is that in the admin UI right now, we're asking the user what label they want to use by referencing the Add x Entries UI, so the label is implicitly plural. That part of the admin UI should be adjusted to simply ask for a descriptor, the idea being that the user will provide a plural one if they are using the default UI, or a singular one if they are using the simple button.