You cant add the restart always tag after you already created the container. You would have to destroy the container and remake it. That sounds bad, but its not, as you can reuse the volumes from the original container, and loose no information. Its done automatically for you with Portainer, as an Edit container feature, but in reality, thats what it does. You could do this with just command line, but it would be a bit detailed, and your volume names are most likely really long names you would never want to type, unless you bound them to the disk, which i doubt you did. If you just created the container, and have very little data to loose, your best bet is to just destoy and remake with tag.
To destroy the container, stop it then remove it.
docker stop kanboard
docker rm kanboard
Now this will leave the volumes, and i am not prepared to go into that, since im on my phone at the moment, but you should learn to use docker if this is your path.
here is a little preview:

you will notice here, i go from KB version 1.2.20 to 1.2.27 by destroying the container, rebuild it, and reusing the volumes, without loosing any data, because all the data is stored in the volumes, as well as my config settings to connect back to the mysql db container, all with 2 buttons Duplicate/Edit
and Deploy Container
, oh and then I had to confirm to replace the container, so 3 buttons:

If you ever go beyond local intranet and want to bring your containers to the internet, here are 2 containers that are a must:
https://hub.docker.com/r/jwilder/nginx-proxy
https://hub.docker.com/r/jrcs/letsencrypt-nginx-proxy-companion
That way you only need ports 80/443, and the proxy will back port everything to the appropriate container through ports 80/443. The LetsEncrypt Companion will generate the TLS certs automatically as well.