The bottom of my (Chromium) window is off the bottom of the screen. If I move the window up, Unity maximises the window (which I do not want).
What key combination can I press to make the active window shorter (smaller)?
Hold down Alt and press space.
Then press R on your keyboard. You can now use the arrows to resize the window.
You can press Alt + F8 and your mouse pointer will automatically switch to a resizing pointer, which you can use to resize your window either with the mouse or using the arrow keys.
You can then click or press esc to stop and turn your normal pointer back on.
I tend to use alt +
middle-drag to resize windows.
It's not pure keyboard but it is useful in awkward situations (like this)
Right-click the title bar, select
Resize and then control the window size with the mouse.
I find Alt + right-click + drag to be the most convenient way to do this.
As there is no mention of the shortcut using super key I will add it. This is complete keyboard shortcut, which has a super key(key with windows symbol). Just press super key + ctrl and then use arrow keys to resize the window. Arrow Up and Down keys maximize and minimize current window respectively.
Bonus Tip: Hold the super key and a short cut menu pops up with all possible short cuts.Tested on ubuntu 14.04 and works on 16.04 also.
The combo is different in Ubuntu (Unity) and Kubuntu (KDE).
Ubuntu 16.04 defaults to Alt + middle mouse button and then drag with mouse.
Kubuntu with KDE 5.8 defaults to Alt + right mouse button and then drag with mouse.
Place mouse on one of the nine edges, and then drag in the direction you want to upsize or downsize.