Shower Door Glide
Hello,
I have a similar center track guide on my Kohler shower doors at home. To remove my center guide, I needed to "lift" up a vinyl strip that runs along the inside of the track to expose the set screw that attaches the guide to the bottom track. The chrome piece at the bottom inside of your track might lift or clip off to expose the set screw but I can't be sure and I don't want you to accidentally damage your shower door track.
The installer left a booklet with me when the door was installed. See if you can find the installation booklet for your door. Also, check the corners of the tempered glass doors to see if the name of the door manufacturer is etched into the glass. You may want to check with a local glass shop or shower door company in your area to see if they are familiar with your brand of shower door.