If you right-click on the file list in the file chooser you should get an option to show hidden files, which makes it possible to add “invisible” paths.
I also understand now that I do not need to specify the WINE path of the plugin. Yarbrige creates VST directories in the home directory, which must be specified in Ardour.
This could be so easily avoided especially for new Users by making ~/.vst a default path in Ardour, there is literally no reason to not do so, please add your voice to this bug report: