lmb = left mouse button
mmb = middle mouse button
rmb = right mouse button

System

open/close editor: Tab
save: ctrl+S
undo: ctrl+Z
redo: ctrl+Y

reload materials, model and map list: F7
reload/apply heightmap settings: F8
print blob count on map: F9
reload language files: F10
reload post processing shaders: F11

Universal

(also works ingame and without developer mode)
emergency restart animator: ctrl+enter
toggle fullscreen: F4
toggle music volume: F5
toggle y-invert: F6

Camera

move camera: mmb drag
hold shift to rotate

zoom: scroll wheel
(hold ctrl to move pivot in/out)

center camera on object: shift+C
align camera to object: zero

rotate: arrow keys
move: ctrl+arrow keys
roll: Q, E
move up/down: pgup/pgdn

Selections

select/deselect: rmb
add to/remove from selection: shift+rmb
select all or none: A
invert selection: ctrl-I

Box select: B, then lmb drag
Press B again for circle select
Use mmb instead to deselect objects

Creating/destroying objects

create object: space
create and copy properties: shift+space
duplicate selected: shift+D
delete selected: X

Transformations

end object transform: lmb
cancel transform: rmb

move selected: G
projective placement: press G twice
scale selected: S
scale positions only: press S twice
rotate selected: R

while transforming objects:
slow transform: hold shift
lock transformation to axis: X, Y or Z
inverse axis lock: shift+X, Y, or Z
use local axis: press X, Y, or Z twice
type number: 0-9 keys, minus, period
paste number: ctrl+V

align objects: shift+S

Linking

link pivot: L
(press L again to reverse direction)

Ingame

move player up: ctrl+H
move player down: ctrl+shift+H

print keys/counters: shift+F1
give all books: ctrl+shift+F2
give and fill bestiary: shift+F2
give magic book: ctrl+T
destroy targets: ctrl+O
revive: ctrl+1
die: ctrl+2
reload checkpoint: ctrl+3

Miscellaneous

cycle pivot mode: comma
set checkpoint: alt+C
Show/hide surface: H
low detail preview: hold ctrl+minus
generate map template: ctrl+shift+M
reload map aux files (books screen only): F3
find objects: ctrl+F