[Tip] So you have cores on someone? Do this.

First off, let me say this is quite cheesy it even works this way at the moment... but oh well, with how limited CBs are fleshed out at launch, we have to make due with what we have dont we? So here goes...

When you have cores outside of your realm, that does not give you some sort of reconquest CB in Eu5 like it did in Eu4, well... not quite atleast. What it does give you is the ability to fabricate regular claims, which once fabricated using 20 spy network strength provides you with a CB that's just way better than the one parliament gives you, not in terms of Antagonism gain, that's the same, but it gives you less warscore cost per location taken.

So here's the trick: With this CB, provinces that aren't cores cost the same warscore and give the same antagonism as your cores... leading to the optimal strategy of counterintuitively taking everything that is NOT a core being more optimal, as now, you can fabricate the same CB again for next war. And like I said before this CB is better than dubious claims from parliament, and better yet... this keeps your parliament free for law changes or CBs.

For example, I used this trick against the Ottomans, Bulgaria and Serbia as Byz, conquering the Ottomans completely before taking my core province of Bolu for example. I never had to waste parliament on any war with these nations.