pgAdmin - How to install "system Tray plugin"?

Question

I use pgAdmin 4 in Linux Mint 19.3.

Whenever I open the program, in addition to the browser, a pop-up appears saying:

Note: Installing a system Tray plugin will Prevent this window being Shown.

I have looked, but I can’t find which plugin it refers to. pgAdmin works normal, but I would like to avoid this window.

Screenshot of the window:

Answer 1

I installed the applet Collapsible Systray and solved.

Now instead of the window, only an icon appears next to the clock.