Annoying ceiling cap hanging always too low made me to make this little clip. As we all know Ikea's things have plenty of place for improvement.
Use 100% infill.
The model was done for ∅5.2 mm cord. You can simply scale it in the slicer to adjust it for different diameters. For example: you have ∅6.5 mm cord, then you need to enlarge the model by 25% (6.5/5.2=1.25).
The inner rounded surface is slightly angled for better cord holding. Use a clip as printed - glossy face downwards.