Where are the rules stored, or can they be exported?
I'd like to transfer all my settings and rules for this extension to another Google Chrome profile. Which files do I need to copy over to the new profile's directory for this to work?
Alternatively, is there an export/import functionality available?
Looking into this also i am hoping we can have this someone added to extension code To store user data for your extension, you can use either storage.sync:
chrome.storage.sync.set({key: value}, function() {
console.log('Value is set to ' + value);
});
chrome.storage.sync.get(['key'], function(result) {
console.log('Value currently is ' + result.key);
});
or storage.local:
chrome.storage.local.set({key: value}, function() {
console.log('Value is set to ' + value);
});
chrome.storage.local.get(['key'], function(result) {
console.log('Value currently is ' + result.key);
});
Found here https://developer.chrome.com/extensions/storage
CustomBlocker has Export & Import functionalities. It is designed to avoid importing duplicate words and rules.

I know synchronizing rules by Chrome sync as @KevsBitcoin mentions is better. Unfortunately, it needs a great change of internal data structure and it's planned to be implemented in the next major update. Sorry for inconvenience.
I don't see the export button. Has this functionality been removed?