Sign up link

Hi!

I have a multi-site wordpress environment, and I’m trying to change one simple thing. The “add listing” page, when not logged in, this shows a text link that says “sign up”

How do I point that link to a page that is on another site of my multisite?

I can choose to set the registration page to a page within the site, but not to a page that points to a page in the multisite network.

Is there an option to change a line of code somewhere in the plugin so that it points to a specific url within my multisite setup ?? ?