To expand on petrilli’s answer:
- Ctrl + Numpad_Multiply can also be used to expand all
- Ctrl + Shift + Numpad_Divide is bound to collapse all
- Ctrl + Numpad_Divide toggles folding on and off
And yes, they can all be rebound, if you know what text to filter on in Windows | Preferences | General | Keys.
“Folding”, “Expand”, “Collapse” are keywords that should get you all of the relevant commands.