This is not a "handy feature," this is a REQUIREMENT for more advanced UI apps. If a VI is inserted into a SubPanel, you cannot open the BD of the inserted VI! If you double click that VI in the project, it simply "blinks" the SubPanel to tell you "Here it is!" You must drag an instance of the VI onto a blank VI, then CTRL+Double Click on the subVI to open up the BD.
I don't know how many times I have really wished this feature was in LabVIEW! I find myself having to open a new blank VI and drop the Main.vi, which is already running with its own menu (so I can't ctrl-E or use the Show Block Diagram), so I can get the Main.vi block diagram open.
Good idea, I can already open the block diagram of a running VI by holding CTRL when double clicking the subVI (with auto-tool off). Having it be consistent with other ways of opening a VI is a good idea.
Add my vote for this. Like wireman, I often want to view the block diagram of a running VI (with custom menu) that I foolishly forgot to open the block diagram of before running. The only way I knew of until today is to kill the running VI, open the block diagram and then restart the VI again, which is often more trouble than it's worth. (I now find myself pre-emptively opening the block diagrams of VIs I'm about to run "just in case".) I also expected to find this option in a right-click menu as fabric.
Now at least I know (from the discussion here) that "all" I have to do is create a new VI, drop the running VI onto its block diagram and ctrl-double-click (hidden command) the VI symbol to get the block diagram to open!