BurpSuite

Adding all Subdomains of a Domain in the Scope

Burp's scope rules use regular expressions in the host field, so you can create a rule that matches something like:

Scope --> Advanced Scope

.*\.test\.com$

If a website has multiple domain names like test.in and test.com, how to add all of them to the scope?

.*\.test\.*$

(^|^[^:]+://|[^.]+.)test.*

https://regexr.com/ is a great resource too.