I use WT on an RPI and docker, with virtual things that I control remotely. As you hinted, it’s stared using host networking…
Did you try to use the IP address of the windows host rather than localhost?
Did you map port 8888 when starting the docker container?
Are there any errors in the logfile when trying to add the virtual thing?
Did you map a persistent volume to store dynamic data, addon code, logfiles so when the container restarts it won’t loose previous configurations?