Comment 2 for bug 1421941

I am seeing similar problem on Ubuntu 18.04.3 vs midori v8.0-31-gf6b3b1e. Midori has scroll bars but no window border to resize. If you right click the titlebar and choose resize you can resize vertically but can't resize horizontally. No private window is required; this is the main midori window. There are some workarounds but these would not be ok at all for a novice user.

Work Arounds:
Windowskey-LeftArrow will make the window half width on left edge of screen and windowskey->UpArrow will make it full screen. Alt-F8 will let you resize the window with keyboard or mouse.