Suitable text editor [NOT word processor] or workaround?

[Richard Owlett <rowlett@cloud85.net>]

My environment is Jessie (8.6.0) with MATE desktop.
I require two things:
 1. a search and replace which can include a "newline" in new string.
 2. display/edit 2 files simultaneously *side by side*

MATE's standard editor (Pluma) can handle the first easily.

I see no way to open 2 instances of Pluma in separate windows - a la 
Notepad in WindowsXP. Pluma will only open multiple files in multiple tabs.

The two files are nearly identical and need them displayed 
simultaneously for instant visual comparison. Opening one of the files 
read only would be acceptable but not preferable.

Suggestions?
TIA