It is possible to set option 119 to a list of domains via the GUI and the list dhcp_option field of /etc/config/dhcp has the correct value after Save&Apply however reloading fails, only the first domain is recovered . A second Save&Apply and the subsequent domains are lost.
119 -> domain1,domain2,etc Save&Apply the GUI refreshes -> only domain1 reappears.
The DHCP-Options field can only be set to numerical values, it would be "nice to have" symbolic values also as in dnsmasq --help dhcp. dnsmasq can handle option:xxx natively no need to translate anything here.