Change group icon according to state – old group style

Hi,
I am not that new to HA, but there is something I just can not figure out.
I have a group which contains all binary_sensors of my window contacts.
The style of this group is the OLD one because I like to see the individual entities when I click on it. AFAIK this does not work when I create a group over the Helper UI menu.

This is my OLD group “Fensterkontakte”:

window_contacts:
  name: "Fensterkontakte"
  entities:
    - binary_sensor.living_room
    - binary_sensor.dinning_room
    - binary_sensor.terrace
    - binary_sensor.office
    - binary_sensor.bedroom
    - binary_sensor.kitchen
    - binary_sensor.bathroom

And for comparison, I have created a NEW group via Helper UI “Fensterkontakte neu”.

On my UI it looks like this:

When I click on “Fensterkontakte” (old group style) I get:

(thats what I want

(thats what I want

When I click on “Fensterkontakte neu” I get:

(thats what I

DON’T

want, because I can not see the state of each sensor

(thats what Iwant, because I can not see the state of each sensor

Both group types have the ability to change color according to the state .
BUT:
only the new group type also changes the icon. Although the old group type also only contains binary_sensors. Here the result:

Fensterkontakte (old one): still closed-icon (although open/on)
Fensterkontakte neu (new on): open-icon

So my question is:
how the heck can I have a group which behaves like the old group style (click on it and see all individual entities) but change the icon according to the state of the group (like the new ones)?
Can’t we have something like “device_class” for groups?

Thanks and greetings!