Thanks! I added that and my connection worked immediately. To summarize, with Qubes 4.2 and Whonix 17 @MrA’s post should work, with the following changes @DVM gives above.
OLD Step 4 (in dom0)
NEW Step 4 (in dom0)
Edit the policy file:
sudo nano /etc/qubes/policy.d/30-user.policy
Add the following line:
qubes.ConnectTCP +18081 monero-wallet @default allow target=monerod