Card-mod trasnparent Card

Please excuse my bad english.

I would like to make the two cards in the Slideschow card transparent.

Unfortunately I am not able to make it. Either the code is ignored or the “slideshow card” is destroyed.

Does somebody has any idea?

type: 'custom:stack-in-card'
mode: vertical
keep:
  box_shadow: false
  margin: false
  border_radius: true
  outer_padding: true
cards:
  - type: horizontal-stack
    cards:
      - type: picture
        image: /cards/security.png
  - type: vertical-stack
    cards:
      - type: markdown
        content: '---'
        title: Offene Fenster und Türen
  - type: vertical-stack
    cards:
      - type: 'custom:slideshow-card'
        fill: false
        arrow_color: White
        arrow_opacity: 1
        auto_play: false
        auto_delay: 4
        style:
          border-radius: 25px
        cards:
          - type: entity-filter
            entities:
              - entity: binary_sensor.Sensor_Garage
                name: Garagentor
                icon: 'mdi:garage'
              - entity: binary_sensor.Schloss_Haustuere
                name: Haustürschloss
                icon: 'mdi:door'
            state_filter:
              - 'on'
          - type: entities
            title: Alles
            entities:
              - entity: binary_sensor.Schloss_Haustuere
                name: Haustüre
              - entity: binary_sensor.Sensor_Garage
                name: Garage