Hi @wildaness,
After a quick check in the theme’s templates, I have found that the text domain for that button is simply “gwangi”.
If you want, you can check that by opening the file located in gwangi/buddypress/members/bps-form-home.php in your theme. The text you’re looking for should be at line 149 in that file.
Hope this information helps you with your setup.
Best regards,