And for watch-only wallet, it's faster and safer to use the master private public key in "Wallet->Information" tab.
I wasn't founding the process, all options weren't quite obvious for it, as the "use a master key" option is just after "standard wallet" option, so "New > Standard Wallet > Use a master key".
Oh, right. That's a typo.
The master private key can't be found in that Wallet menu anyways, so some will get it right away.
I'll edit my reply to fix that. Thanks for pointing that out.