Actually, ... it is done like this:
Tap the "+" to Add Wallet, then tap the Lightning button 10 times.
Voila, you can then create a wallet via LDK!!
You can then open a channel to it.
I've not done it ... yet.
But wanted to share this here on SN after seeing it on birdsite today [Nitter]. This may come in handy, especially since BlueWallet is sunsetting their LNDHUB (recently postponed until May 31st, 2023). I'm just the messenger, so if this has a flaw or something... I'm not vouching for it.