Add things to left sidebar - How

Configuration Frontend
1

I have moved Zigbee2Mqtt and mqtt outside of HAOS on my proxmox install.
How do I add stuff to the menubar/left sidebar in the normal HA view ? Just like the addon would do it ?

Now, if I need to access things from the outside, I assume having a different IP/hostname for an IFRAME would be problematic. Is there an official way to handle this ? Say a reverse proxy Addon - lustening on some port x, and on that one I would be able to map things to the host behind HA ?

2

Found out there is a zigbee2mqtt proxy - Thus moving it out is getting commong.
Now next it to make one that works for frigate with everything included.