So I can be viewing two documents side by side? ... Yes? (i.e., with both documents in TextMaker)
Yes, you can!
Two, three, four, or as many as your screen real estate will yield.
But I can't drag a paragraph from one to the other?
No, this isn't possible.
How about dragging to/from another word processor? Will that work?
The result will be an OLE-object (if the other word processor is OLE-enabled, e.g. Word). So, for simply copying text, you're back at copy & paste.