Invert selection: sometimes you need to select all items in one folder but a few. The best then would be to select the ones you don’t need and then hit Edit>Invert Selection (alternatively, hit Alt+E+I).
Status bar: available under View>Status bar. It shows the number of items or selected items under a given folder. Useful to check you are not missing files in large projects.
Search feature: ever happened that you had to perform a task (like analysing, pre-translating or cleaning files) on files scattered in a complex folder structure? You can do it by going to the root level and running a search by *.[file extension, e.g. rtf, ttx]. All files will show in the same screen. Drag and drop them in the window of your CAT tool and you are good to go.