How to search for all tasks in MS Project file?
You can't. By default MS Project is searching for only expanded tasks. So it is obvious to expect search dialog to have checkbox for all-nodes search.
But looks like there is no such checkbox so you always have to expand.
Instead of the checkbox the search dialog has pretty much only two combos: "Test:" and "Field:" ("Search:" has just "Up" and "Down") :
Maybe it's just me but they look funny and probably used only for about 0.1% of the searches people do? :)
PS! Should we be worried when project file size suddenly drops from 1MB to 400KB but all information is still there?