Sidepanel links to nginx proxy manager and uptime kuma (already have one for Rachio that works)

So I am running HA on a Raspberry Pi 4 right now (I plan to get an HA Yellow when there is more availability), and I followed the Rachio Integration Docs and have a link that launches the Rachio app in an iframe within HA. I want to do the same for Nginx Proxy Manger and Uptime Kuma. Is this possible? I tried adding the entries underneath the working Rachio entry in my configuration.yaml, but it does not work and throws errors.

FYI: I have only been trying to write YAML for about a week after working thru a short tutorial. I have a feeling it is a limitation with panel_iframe, but I can not seem to find enough information on the options to verify my suspicion. I searched other posts, but they all seem to want to access menu items within HA.

Any help is appreciated.

from configuration.yaml (non-working items commented out obviously):

panel_iframe:
  rachio:
    title: Rachio
    url: "https://app.rach.io"
    icon: mdi:sprinkler-variant

#  uptime-kuma:
#    title: Uptime Kuma
#    url: "http://172.16.0.254:3001"
#    icon: mdi:state-machine

#  nginx-proxy-manager:
#    title: Nginx PM
#    url: "http://172.16.0.254:81"
#    icon: mdi:state-machine