Hello,
Thank you for the question and I am very sorry about the issue!
From my experience, the slowness does not come from the number of layers, but the content inside the layers and how they intersect with each other. Make sure to assign correct
Layer Intersection Group for elements that should not intersect with each other. You can also use the Attribute Manager to purge any unused layers.
If this does not help, I would like to have the file for further investigation. Please let me know if it's possible and whether you need a secure place to upload the file also!
Looking forward to hearing from you!
Best regards,
Minh
Minh Nguyen
Technical Support Engineer
GRAPHISOFT