The ability to select multiple models works in 4.20 and earlier. From there you can right click and align, distrbute, etc. I just opened issue #355 for this.
You can manually edit the X,Y locations in the xlights_rgbeffects.xml file. Backup before you do.
Arrow keys for layout is a common request, but you can do it yourself, no programmer assistance needed.
Before proceeding, make sure the Num Lock feature is toggled on by pressing the key until you see an indicator light, or can type numbers with the keypad.
>>>Shortcut in all versions of Windows<<<
Press Left Alt + Left Shift + Num Lock on your keyboard at the same time.
When the window appears, press Spacebar or Enter.
Repeat this process to turn Mouse Keys off.