Better selection in CAS expressions

[marcin1812]

Didier:
Yes, I know Copy/Paste is working, but... this is not effective and a bit primitive.

Prime has a great hardware, but soft sometimes can't keep up with hardware.

In my opinion "left" should split selection to smaller part of expression, then up/down should move to the next parts of expression.

30 Years old Derive for DOS was it well resolved
So there are old good examples, and no need to reinvent.

Regards