gnome-shell-extension-top-icon software package provides GNOME Shell extension to move system tray icons to top bar, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gnome-shell-extension-top-icon
gnome-shell-extension-top-icon is installed in your system.
Make ensure the gnome-shell-extension-top-icon package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnome-shell-extension-top-icon*
You will get with gnome-shell-extension-top-icon package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | GNOME |
| Package | gnome-shell-extension-top-icon |
| Version | 17-01-16 |
| Description | GNOME Shell extension to move system tray icons to top bar |
| Sub Section | gnome |