Hold Shift to include objects into a selection and Ctrl to exclude objects from a selection.
Press Alt (or AltGr) to highlight adjacent connections of the node under mouse cursor. (Note that in Linux Alt is often reserved for window drag-and-drop operation. Also, if used remotely via Exceed, by default Alt is taken for local and its presses are not passed to remote.)
Outline a selection rectangle from-left-to-right for adding objects that are inside the selection region, and from-right-to-left for adding objects touched by the selection region.
Press Crtl+A to select everything or Ctrl+I to inverse the selection.
Use left mouse button or ←, ↑, →, ↓ to move selected components.
Press Delete to remove selected components.
Press Ctrl+A to select all objects or Esc to reset selection.