Centering all windows in XFCE

[bitsnpcs]

Hello forneus,

task 1 -

Menu>All>Window Manager Tweaks

Select Tab "Placement"
Tick Radio button "At the center of the screen"
Click "Close" button

Task 2 -

Experimental ( I haven't tried it), if you also want the windows to overlay each other and not fill up the entire screen.
Menu>All>Window Manager
Advanced tab
"Windows Snapping", tick box "to other windows"
click close

If it doesn't overlay return to Menu>All>Window Manager
Advanced tab
"Windows Snapping" and  remove tick "to other windows"