Edit:
I solved it by myself, I have V2.0.80 and therefore used the wrong blueprint. Thank you anyway. 
2nd edit: here’s the template that I‘m using successfully until today (HAOS, ZHA, Shortcut button firmware 0x24040006)
https://community.home-assistant.io/t/zha-ikea-tradfri-shortcut-button-firmware-2-3-075-or-greater/402565
Hi there,
Thank you for the blueprint.
Unfortunately I run into this error:
Message malformed: expected a dictionary for dictionary value @ data['action'][0]['variables']
Is it just me or does anyone have a clue what I could have done wrong?
Thank you in advance! 
Micky
Edit:
I solved it by myself, I have V2.0.80 and therefore used the wrong blueprint. Thank you anyway. 
2nd edit: here’s the template that I‘m using successfully until today (HAOS, ZHA, Shortcut button firmware 0x24040006)
https://community.home-assistant.io/t/zha-ikea-tradfri-shortcut-button-firmware-2-3-075-or-greater/402565