I uploaded a map to Trackmania Exchange a few weeks ago, but it turns out there are a few bugs. I fixed a camera issue and added a few more blocks to keep cars from flying off of the track. (original map link - https://trackmania.exchange/maps/178369/little-pasta)

What is the correct way to re-upload this map to TM Exchange? When I update files, I'm told "This track already exists.". Is there a way to do this, or do I need to hit 'Delete Map'?

Go to your map's page. There should be a button labelled "Update Map File". That'll let you upload the new map file.

If you're still seeing "This track already exists", then your file might be caught partway in the upload process. I believe there should be a portion of the map upload page at the top that lets you resume or cancel partial uploads.

Thanks Arkive86!

It might have been a wifi issue on my end, but I was finally able to replace it with the instructions you gave - thank you for the help!