So, let's clarify that: asking XenForo for assistance for having modified things on the database side, is like not having an active subscription. So please be advised it is very dangerous and you are advised to be very cautious.
---
In my case I do this:
I access the main page of Mysql
I do as if I am renaming the database
But instead of renaming it, I click the backup link, which appears in the pop-up window.
I do this, because in my case, it appears to be automatically and correctly compressed, and it is much faster to download.
Yes, I also know, that through phpmyadmin I can make a compressed backup, but it is much much slower, even if compressed.
So, this procedure (again in my case) is much faster for me to download a database even if it is large.
If anything, give it a try, and let me know if it's faster for you too.