Credit: I learned this part from a Youtube video of André Biedermann which uses GMapTool and TYPViewer to extract, change, and merge TYP files. On this page I only made the bare minimum of screenshots to help you along. For a more detailled overview I recommend you watch his video. He talks German, but his video is so clear it should be easy to follow nonetheless.
I am using a free map of Cyprus from OpenTopoMap for this tutorial
Choose the directory where you want your TYP file to end up, and choose the option to create a TYP file
If you see this screen you’ve successfully extracted the TYP file from the map. In my case it’s called “XOPENTOP.TYP”, you can of course rename it to whatever you please