Key 'card_mod' is not expected or not supported by the visual editor

[tnj (Tom)]

I have just started using the card mod after installing through HACs. I have the following lines in config.yaml

frontend:
  themes: !include_dir_merge_named themes
  extra_module_url:
    - /hacsfiles/lovelace-card-mod/card-mod.js?hacstag=190927524410

The same url is showing in dashboards-resources.

I have entered the following in a dashboard for an entity and the entity text colour has changed to blue but I get a warning when trying to edit the secondary information.

entity: switch.up111_rtl_15_socket_1
secondary_info: last-changed
name: Dummy LED TV
icon: mdi:television
card_mod:
  style: |
    :host {
      color: blue;
    }    

**Visual editor not supported**
* Key 'card_mod' is not expected or not supported by the visual editor.
* The provided value for '' is not supported by the visual editor. We support (string) but received ({"entity":"switch.up111_rtl_15_socket_1","secondary_info":"last-changed","name":"Dummy LED TV","icon":"mdi:television","card_mod":{"style":":host {\n color: blue;\n} \n"}}).
You can still edit your config using YAML.

I also do not get the little brush icon next to “show visual editor” as mentioned in the read me.

[JulianDH (Julian Hall)]

@tnj

secondary_info: last-changed

Secondary info From a different Entity

hello. i have cover set up and i would like to show the window (binary_sensor) status open or closed in the secondary info from the cover entity. i tried something like this: entity: cover.bed_room_bed secondary_info: binary_sensor.bed_room_small but nothing shows. is it possible?

[Ildar_Gabdullin]

@tnj

have entered the following in a dashboard for an entity and the entity text colour has changed to blue but I get a warning when trying to edit the secondary information.

You probably mean Entities card.
The “visual editor not supported” warning is shown when you get to yaml editor for a particular entity row:

But it is not shown when you are editing a whole card:

In short - do not bother about that warning. Card-mod is a 3rd party plugin which may cause such glitches.

[dcapslock (Darryn Capes-Davis)]

@tnj

I also do not get the little brush icon next to “show visual editor” as mentioned in the read me.

FYI: The style brush got lost when Frontend updated buttons during in 2025.8. 4.2.0 will bring back the style brush by upadting how card-mod finds the button to add the brush.