Preface: there are apparently 2 types of these USB H-Shifters, ones that use hall effect sensors like mine and ones that use actual button switches. I cannot confirm if this will work on the one that uses switches but it might. The amount of travel the clip allows appears to be enough to just let the clip hit the switch before returning to a neutral position. This clip redesign is for the hall effect switched version.

This is a clip or replacement clip for the USB H-Shifter that enables the shifter to operate as a sequential shifter. The unit I bought off Amazon is the Aikeec USB Shifter 7 + R which came with the sequential shifter clip but this should even work for the 6 gear version (I think). The problem I have with the original clip that came with the unit is that it requires a tiny nut and bolt to be used to secure it in place and that it slowly works itself up the shifter shaft. I designed a replacement clip that doesn't require anything to secure it in place and won't ride up the shifter shaft. To install the replacement clip, pull the magnets out of the stock clip, insert them into the redesigned clip, and then install the clip onto the shifter in the sequence pictured from 1 to 3. Removal is the reverse of the installation. I printed it on it's side with the open side up without supports like how pictured in Cura but you can use supports if you want.

If you don't have the original clip and need magnets, the magnet that came with the clip I modeled the design around measures 3.9mm x 7.5mm. This is the closest I could find on amazon. Might have to drill out or open the hole a bit to get the magnet to fit.
https://a.co/d/8imcxQN

Here's a link to the USB H-Pattern shifter I bought:
https://a.co/d/62ODleY