While you wait for answers, we may have found some information which could help you.
Click here for Blinds Blind Cordhow can i shorten the width of my levolor vertical blinds?
Replacing cord for high Velux window?
How to retension a Velux blackout blind GGL4?
I need to shorten draw strings ?
How can I fix my velux blackout blind GPL 308 with broken cord?
Where can I get velux blind cord from?