A few more XML.xml layout details

in an XML layout file if you had a XML line like <div id="main-disp" src="flexyFileContent"/>
That would mean the DIV element whose id is main-disp would display the output generated by plugins/flexyFileContent.php
Among other things that means that content would be encased in a block element named main-disp, probably styled by CSS codes in css/robo.css

An XML layout might contain codes like this:

<div id="main-disp" src="flexyFileContent" > 
      <div id="toc" src="dynamicNaviation" />/
</div>  

The XML above places the output from plugins/dynamicNavigation.php inside the boundaries of the block element DIV whose id is main-disp. But that also means the content from dynamicNavigation is contained within a block element DIV (inside main-disp) whose id is toc.
Block elements contained within block elements (toc inside main-disp) carry some layout baggage. Perhaps what you really want is for the contents generated by both flexyFileContent.php AND dynamicNavigation.php to be displayed inside main-disp, without a block element boundary around the content generated by dynamicNavigation.php

To do that the src attribute can be used to specify one or MORE plugins as content generators, as a comma-delimited value.
For Instance as:

<div id="main-disp" src="flexyFileContent,dynamicNavigation" /> 

In the exapmple above the output generated by dynamicNavigation might be a series of rectangles containing thumbnail images and a bit of text, packaged as a hyperlink. If all those small recatangles were told by CSS to float: left; that could be used a convenient gallery layout, where rectangular thumbnails surround a main display image.