Selection, past and text
CTRL+A     Select all
CTRL+C     Copy image or selection
CTRL+D     Show / Hide selection
CTRL+E     Show / Hide the image explorer
CTRL+G     Show manual settings window for the selection
CTRL+I     Invert selection
CTRL+T     Add text
CTRL+V     Paste clipboard contents

MAJ+CTRL+V     Paste clipboard contents as a new image
SUPPR     Delete selection and replace with the fill color
CTRL+X     Cut the image or selection
ESC     Cancel paste or text / Hide selection
ENTREE     Validate paste or text

A     Rectangle selection
B     Ellipse selection
C     Rounded rectangle selection
D     Rhombus selection
E     Bottom base triangle selection
F     Left base triangle selection
G     Top base triangle selection
H     Right base triangle selection
I     Lasso selection
J     Polygon selection

Arrow keys (*)     Move the selection one pixel at a time
SHIFT+Arrow keys (*)     Move the selection eight pixels at a time
Dbl-Click     Show / Hide the bounding box
CTRL+Dbl-Click     Transform selection to paste
MAJ+CTRL+Dbl-Click     Cute and transform selection to paste

(*) Arrows keys (UP, DOWN, LEFT, RIGHT)
The ALT key can be used in combination with the arrow keys to modify the size of selection.

Adjusting image view
CTRL+F     View in full screen mode
+     Zoom in
–     Zoom out
0 (zéro)     Automatic zoom
1     Actual image size

Navigation keys (in the current image folder)
Home     First image
PgUp     Previous image
PgDn     Next image
End     Last image

Image Manager
SHIFT+CTRL+C     Copy image to
SHIFT+CTRL+M     Move image to
F2     Rename image file
SHIFT+DEL     Delete the image (sends to the Recycle Bin)

Cf. How to use PhotoFiltre | PhotoFiltre Masks | PhotoFiltre Main Page