I want to make some large reordering of my text, wich means a lot of copy/paste work between distant chapters. I was wondering if it is possible to make TexMaker display the source viewer twice on my Screen, one next to the other, maybe instead of the Pdf viewer. Then I could have both relevant spots in my document on screen and easily copy-paste content without scrolling my finger into oblivion. It would have to be possible to scroll both sourceviewers independently.
Use the Source Viewer panel
As of texmaker 4.1.1, viewing two source files side by side, both of them in read/write mode, is not possible. However, texmaker allows you to open one source file in read- only mode in its so-called Source Viewer panel, precisely for easy copying & pasting between that file and other source files open in regular, read/write mode. The screenshot below is taken from the official texmaker page.
To open a file in read-only mode, simply click the Source Viewer button (located at the bottom left of the screen), press the Open icon in the Source Viewer that just opened, and browse for the file in question. This video shows the steps to follow.
To answer your question more specifically, nothing prevents you from having the same source file open in read/write mode (on the left) and in read-only mode (in the Source Viewer panel, on the right) at the same time.
Additional tips for quick navigation
As mentioned in the comments, and since you asked me to expand on it, I use TeXworks only for the editing of the following files:
For the remaining part, I code everything in n++ with no particular plugins, each chapter/figure/table in its own dedicated
Pros of using n++: