In the early model A1, A2 and A3 platform VW Rabbit, Scirocco, Jetta, Convertible and Pickup/Caddy models with the 020 transaxle, adding weight to the longer sift rod can help improve shifting feel. In fact, so much so, that in the A3 models, VW included a weighted shift rod. The weight adds mass/momentum to the shift rod to help push the transaxle into the next gear. This is a great help, especially if the shifter throw has been shortened. With the shorter throw, the driver has less leverage on the shift linkage and the added mass can help overcome the loss of leverage. Plus, the all metal rod ends replace the sloppy plastic bushings the factory used.

OpenSCAD file includes customizer parameters to make the various versions of the shift weight.

This model can be used to create a clamp on weight or a machined billet weight with ball stud rod ends, as seen in the first photo. These can replace the factory plastic bushings on the shift rod with all metal ball studs rod ends, similar to these:
https://amzn.to/4qOLv1v
The ball studs are 13mm diameter and the sockets use M8-1.25 thread.

Fabrication methods include cutting a length of steel or other heavy material and clamping that to the factory shift rod. A second method would be to cut a similar length of material and then drill/tap the ends for M8-1.25 female thread and insert M8 threaded rod or skip the threading and just weld on the threaded rod or a short M8 bolt. Finally, the full length weight can be cut, ends machined down to 8mm diameter and then threaded, as see in the second photo.

The third photo shows the A1 billet weight installed and the fourth photo shows an A2 or A3 billet weight installed.

1" diameter steel rod works well:
https://amzn.to/4s4DpD2
or for the shorter A2/A3 weights, 1-1/4" retains the weight in the shorter length:
https://amzn.to/4kQTh9Q
If machining the material, use mild steel or a free machining type alloy. Something like brass could also be used. Lighter materials like aluminum or plastic would not be ideal. However, you could 3D print a part to use as a pattern to machine a metal part from.

More information:
https://www.4crawler.com/Diesel/ForSale/ShiftLinkage.shtml