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Go to your user account in Figma, and go to settings. Scroll down to Connected apps, there you will see Figma Connect. Click Revoke access to disconnect the app.
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Why is it only those who share Figma files who needs a Figma account?
Litt mer teknisk svar her vil jeg tro 
Må også se på formuleringen på spørsmålet 
The URL for sharing I get from Figma is not working
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