How to run Thunderbird inside thoroughly?

> The following exclusions allow Email readers running in this sandbox to access mailbox files outside the sandbox.
Does this setting mean such apps can change the corresponding files outside?

But I want to test different versions of Thunderbird inside sandboxes thoroughly, without changing anything outside.
Is it possible?

I guess a local template might do.
But after reading Templates.ini, I'm not sure I can make one by myself.

I need help.
Thank you.