Add «Save Window Positions _Now» to <image>/Windows menu

Description of the feature

Add a menu item to the "Windows" menu that does the same thing as the Save Window Positions Now button in Preferences.

Use cases

I don't use "Save Window Positions on Exit" because I often move windows around in a way that I don't want to save.

However, I regularly come up with better layouts and want to save my window positions.

Currently, that means 4 clicks: /Edit/Preferences/Window Management/Save Window Positions Now ... and I have to remember where the option is hiding!

I would prefer 2 clicks. 😃