This extension lets you toggle night-light from the top-bar by clicking it.
It seems like doesn't work because there are no color changes on demo.gif but this is just because screen capture doesn't capture night-lighted output. So, it works.
To make this extension much powerful, you can set a manual schedule from gnome settings like this.
Setting the "From" and the "To" as the same value allows you to use night-light anytime you want with a simple click on the extension.
git clone https://github.com/cansozbir/gnome-shell-toggle-night-light-extension
cd gnome-shell-toggle-night-light-extension/
cp -r [email protected]/ ~/.local/share/gnome-shell/extensions/
After restarting your gnome-shell by pressing Alt+F2 and entering "r" or with login after logout, you can enable the extension from the gnome's extensions app or gnome-tweaks app.