I've tried to add the extension "sense-navigation-master" by stefan walther. After I removed some duplicates inside the folder it uploaded with no problems. But then I wanted to change the color options in the extension which lead me to edit it in the developer hub. There I get the "wbfolder.wbl file is missing" error.
And when I check the extension it doesn't exist a .wbl file, so I guess that's the problem.
Next step is of course to google it, which I did. I came to the conclusion to use the wblgen.bat file made by Nate untiedt
Is this server or desktop? In desktop putting the file in the right place (same as qext file) should work. In server you need to put it in the zip file and re-import. Just adding files on disk does not work.