I always wanted a spool with the following features:

• lightweight but still strong enough
• holds at least 15 m strong , thick cord
• can fit the thumb in the middle hole even when wearing a neoprene glove
• compact enough to form a loop around it using the thumb and forefinger

Designed in Autodesk Fusion 360. The design is parametric: change h_spool parameter to set the width (or height - as you wish) of the spool. There is a 30 mm wide version on the photo with 13 m long, relative thick (~=3 mm) utility cord.

To assemble just screw the two halves together. The thread is long enough to hold properly but if you want to fix it just print from ABS and dip the male thread in acetone first.

Update #2024-07-09: Fusion 360 source file uploaded.

Update #2024-07-18: based on user feedback I have expanded the female threads in the model by 0.1 mm.