Where to find my owner private key ?

I've noticed that after creating an account, switching to permissions - I can't access my owner private key.
While a couple weeks ago, it showed every private key after unhiding it.

So how can I get and securely store it somewhere, when I can't even see it ?

Could someone please tell me where to find it now ?
I guess I'm not the only one with this issue :/

Thank you in advance !