Thank you Skif-off,
I copy&pasted the first sript from your link into a new file and saved it as
LinesSelectCopyMoveDuplicate.js
Read various help rescources and figured out where to put the scripts folder.
Basically, I got it working - to some degree - by right-clicking in my text, choosing
Scripts > Scripts .... > Exec > picking an entry from the context menu, typing into the dialog field....
However, this is still a far cry from the Alt up/down shortcut I had hoped for. Would you please guide me towards setting up such shortcuts, if it's possible at all? Been reading and racking my brain but this is just over my head. 
 
