Yes, exactly @Johnny_Fartpants .
Setting an IP address works, but domain names are better manageable for network administration and human-readable for documentation purposes.
In the popup for “Hosts allow” they also state "Enter a list of allowed hostnames or IP addresses. " (emphasis by my; or do they mean old netBIOS names?).
I found What is the official way of modifying auxsmbconf field of smb share now? , which is related and recommends to use the command line with cli. But isn’t this tool legacy, too, so I would need to use another command midclt?
And with both solutions there are probably issues with persistence and visibility in web-interface.
I can’t believe they disabled all Samba auxiliary parameters, without providing any alternatives to admins - oh dear.