Can geostationary satellites be seen from the earth ?
The answer to this question was Yes. Use a fixed camera and a long time exposure.

Example image
Geostationary satellites as seen from the earth.
The horizontal streaks are the background stars slowly moving across the fixed camera view, over an exposure period of several hours.

This comes from https://noirlab.edu/public/news/noao0106/

Question now : Does anyone know of software that will show the location of geostationary satellites against a background of the visible night sky stars.