Where is the json with the Loot chest configurations stored?

Unless you've saved the loot JSON as the default, it should be located in the world directory under QuestLoot.json

If you're looking for the default loot file, that would be in /config/betterquesting/DefaultLoot.json

Can I take the QuestLoot.json in the world directory, rename it to DefaultLoot.json and put it in /config/betterquesting/ and make that the default loot in the pack?

@Funwayguy not sure if you see this since you closed it

There's a command that can do that for you. It should be something like:

/bqs_admin default
or
/bqs_loot

Not at the computer at the moment to check

Will try that, thanks.
It was /bq_loot default save