Cutting by hand

Select any stretch and cut it, or bring it back.

Select a stretch on the timeline by dragging, or with I (start) and O (end) at the playhead.
Press Delete.

A cut stretch can be brought back: select it and press Delete again, or use the restore action on the stretch itself. Any action can be undone with ⌘Z (Ctrl+Z).

Getting around

Wheel, pinch or vertical swipe — zoom around the pointer.
Shift + wheel or a sideways swipe — scroll.
Bookmarks: B to add, Shift+[ / Shift+] to jump.
Esc clears the selection.