Ubuntu 18.10 Meld missing preferences option

Solution 1:

The preferences menu has moved to the top bar just next to the Activities badge. This is not only true for meld but also for many other GNOME applications, e.g. gedit.

I don't know why they did it and consider it totally useless and counter intuitive, but that's how it works.

Solution 2:

1. sudo vim /usr/lib/python3/dist-packages/meld/meldwindow.py (or, instead of vim, use any other text editor)
2. replace
   if not gtk_settings.props.gtk_shell_shows_app_menu:
   to
   if gtk_settings.props.gtk_shell_shows_app_menu:
3. Profit!

Works on Ubuntu 19.04

Solution 3:

I fixed it by installing gnome-tweaks and disabling "app menu" under "top bar".