Help with variables in a button-card

Configuration
,
1

Well I have a button-card that has a honeycomb and one of those options is to redirect to another url to see more info. but it’s an url that for confidence needs to get saved in a variable first, and get invoked when I will need it in my HA so how can I save that variable

hold_action:
  action: call-service
  service: honeycomb
  service_data:
    active: true
    buttons:
      - show: false
      - icon: mdi:chart-bar
        color_type: card
        color: green
        tap_action:
          action:
            service: browser_mod.navigate
            data:
              url: // I want the variable here
      - show: false
      - show: false
      - show: false
      - icon: mdi:wrench-clock
        color_type: card
        color: >-
          [[[ if (states["switch.k3sregistry_mantenimiento"].state == 'off')
          return "yellow"; ]]]
        style:
          width: 1%
        tap_action:
          action: call-service
          service: switch.toggle
          service_data:
            entity_id: switch.k3sregistry_mantenimiento

I tried in my configuration.yaml

default_config:
 variables:
  my_url: "http://example"