GNOME shell doesn't detect custom .desktop file

Question

According to official guide, gnome launcher supports to see and display custom .desktop file in these two paths:
/usr/share/applications
~/.local/share/applications

But no path above works. I even restart OS but nothing change. I also try to locate some sample .desktop in gnome launcher including built-in apps and new apps (openToonz). Here is a path I have found:
/var/lib/snapd/desktop/applications

Apparently, I copy my .desktop to the path above and waiting... in void.

What did I do wrong? Below is the content inside my .desktop

[Desktop Entry]
Name=OALD
Comment=Open OALD online in Firefox
Exec=firefox "https://www.oxfordlearnersdictionaries.com"
Icon=oald.png
Type=Application
NoDisplay=true
StartupNotify=true
Categories=Education; Network; Dictionary;
Keywords=dictionary;internet;web app;
Actions=private-mode


[Desktop Action private-mode]
Name=Open in Private Mode
Exec=firefox -private-window "https://www.oxfordlearnersdictionaries.com"

Btw, my .desktop is a link opened by Firefox.

Answer 1

The only thing wrong with your .desktop file is the following line:

NoDisplay=true

NoDisplay=true means

this application exists, but don't display it in the menus.

So either remove this line or change it to

NoDisplay=false

Then put the .desktop file in ~/.local/share/applications (only for the current user) or in /usr/share/applications (for all users).