I mean something like this:

No I do this manually by adding more "node" tags inside the project.gaia file:
<node label="source" checked="0">
<node label="assets" icon="flashFileIcon" checked="0">
<node label="assets.fla" icon="flashFileIcon" checked="0" src="assets/assets.fla"/>
<node label="fonts.fla" icon="flashFileIcon" checked="0" src="assets/fonts.fla"/>
<node label="background.fla" icon="flashFileIcon" checked="0" src="assets/background.fla"/>
<node label="videoplayer.fla" icon="flashFileIcon" checked="0" src="assets/videoplayer.fla"/>
<node label="preloader.fla" icon="flashFileIcon" checked="0" src="preloader.fla"/>
</node>
<node label="adventure" icon="flashFileIcon" checked="0">
<node label="adventure.fla" icon="flashFileIcon" checked="0" src="adventure.fla"/>
<node label="adventures.fla" icon="flashFileIcon" checked="0" src="adventures.fla"/>
</node>
<node label="create" icon="flashFileIcon" checked="0">
<node label="create.fla" icon="flashFileIcon" checked="0" src="create.fla"/>
</node>
<node label="tools" icon="flashFileIcon" checked="0">
<node label="tool.fla" icon="flashFileIcon" checked="0" src="tool.fla"/>
<node label="tools.fla" icon="flashFileIcon" checked="0" src="tools.fla"/>
</node>
<node label="showroom" icon="flashFileIcon" checked="0">
<node label="showroom.fla" icon="flashFileIcon" checked="0" src="showroom.fla"/>
<node label="product.fla" icon="flashFileIcon" checked="0" src="product.fla"/>
</node>
<node label="other" icon="flashFileIcon" checked="0">
<node label="home.fla" icon="flashFileIcon" checked="0" src="home.fla"/>
<node label="index.fla" icon="flashFileIcon" checked="0" src="index.fla"/>
<node label="intro.fla" icon="flashFileIcon" checked="0" src="intro.fla"/>
<node label="introduction.fla" icon="flashFileIcon" checked="0" src="introduction.fla"/>
<node label="navigation.fla" icon="flashFileIcon" checked="0" src="navigation.fla"/>
</node>
</node>
It would be nice if Gaia does this for me