Drop down menu for - Are you reporting a ticket for a specific site?

When you click to Submit a New Ticket on the Support page, there is a drop down menu with text that says "Are you reporting a ticket for a specific site?". Listed is "Default Site" and then the main site of the network.

I am using the Membership 2 plugin and have manually added a Test user to a Membership Level. When I login with that user to test the Ticketing system, I only have the two site options listed above (Default and main support site). I'm guessing that if I create a sub site on the Multisite install for a new user, when they are logged in, their site would be listed instead of the main site?

Is there a way to manually add sites to this drop down menu? For example, I have clients with stand alone WordPress websites separate from my Multisite install. I want to use this Support page to manage tickets from all of my clients including those with self hosted sites and sites that are part of the network. It would be nice if their site showed up in the list, but only their site and not a listing of all sites.

Is the drop down menu being populated by the Memberships plugin, or is it pulling the associated website from the user profile?

Along with this, if I can't change the way the drop down works, I'm guessing I could probably just hide it with CSS?

Is it possible to add an additional form field to the ticket form where maybe they could manually type in their site url?

Very specific questions I know, any direction would be appreciated.