See bug #166270 comment #8 for some background.

Proposal: omit top-level nodes in Files corresponding to descendants (possibly indirect) of another top-level node. Thus, if an aggregator (pom-packaging) project were opened together with some or all of its component modules, there would be just one entry at top level; the same would apply to e.g. Ant-based EAR projects with nested EJBs and WARs. In such a case it might be useful to add some sort of notation to subfolders which are project directories showing the project display name in gray, e.g.

Files
-----
+ /home/jglick/src/stapler (Stapler POM)
|
+- core (Stapler)
|
+- groovy (Stapler Groovy module)
|
+- jelly (Stapler Jelly module)
|
+- jsp (Stapler JSP module)
|
+- pom.xml
|
+- src


Notes:

1. Select in Files would still work; you might be taken to a more deeply nested tree node than now. (The current behavior is to select the node starting from the nearest open ancestor.)

2. There would still be separate top-level items for external source roots. (Rarely used for Maven projects, but common for Ant-based projects "...from Existing Sources".)

3. If the POM in the above example were closed, but the four submodules remained open, the one top-level item would be replaced by four. Closing or reopening any of the submodules while the POM was open would have no visible effect in the Files tab.

4. VCS status (e.g. Subversion modification badges) would be displayed more naturally than is currently the case.

5. Length of node labels may be a problem for top-level nodes, since OS paths can be lengthy. This is already a potential problem in the case of external source roots but would now affect many more people. Could perhaps show just project display name as now, with the path available in a tool tip, or show path after the project name so that any truncated text is in the path part.