Turns out this is pretty simple to implement. It requires editing core files - which means it'll probably be lost one day on upgrades. I have no idea if this can be done with a community app, but this is at least a beginning for us who are used to docker-compose but still able to use the dynamix docker manager web interface.
Tested this in version 6.9.2
I take no responsibility if you break something. Make sure you have a backup of this file before you begin.
It would be great to see this included in the core of unraid since it's such a simple addition.
Edit /usr/local/emhttp/plugins/dynamix.docker.manager/include/DockerClient.php
Look for public function getAllInfo($reload=false) { and at the very end of the foreach add:
if ($ct['Icon']) $tmp['icon'] = $ct['Icon'];
if ($ct['url']) $tmp['url'] = $ct['url'];
Look for public function getDockerContainers() { and inside the foreach, beneath the line containing $c['BaseImage'], add:
$c['Icon'] = $info['Config']['Labels']['net.unraid.docker.icon'] ?? false;
$c['url'] = $info['Config']['Labels']['net.unraid.docker.webui'] ?? false;
Clear browser cache and reload the unraid web ui. Icons and webui links from unraid templates still work, and those from a docker container label also now work.