In my bedroom I am using two sets of three Ikea panel curtains as the closet doors. When I purchased these, they came with parts that interlock the panels so that when you pull one panel, the interlocked panels follow it to open or close. You can also see this part in this video

My problem with these however was that the amount of panel that would overlap because of the part made the three panels just a little too short to completely cover the closet. So I initially tried to just cut the part to make it shorter and decrease the gap.

This worked only for a short while though, and the connectors didn't stay in place from the force of pulling and pushing two panels. So I wanted to design a part that I could attach more securely and was also shorter than the original one.

After a lot of trial and error, I feel I have something I am satisfied with. This is a two part solution that relies on M3 nut and screw. There is a captive nut piece that you slide into the track with an m3 nut inside it and then you screw in the connector piece and tighten.

The new fitting is a little wider to ensure that the curtains catch each other and they won't slide around when screwed on tightly.

The screw hole on the connector piece employs a technique that tries to prevent the printing of 90 degree overhangs. So you will have one thin solid layer that you will have to force the screw through when assembling.