I think key combination 'Cmd+4' should be changed to the combination which is set in Preferences-General-Keys-Content Assist(Ctrl+Space on Windows). You could also create your own content assist subtype. Also about filtering Max mentioned. Actually there are sould be 2 features:
- Show commands which starts from the already entered text in console in the shell
- Reveal to the command on typing like for example standard combobox do