Basically, there are four areas, and on each area four actions are possible:
# Horizontal header
#- click: switch time + select frame of the current layer
#- rclick: menu (insert/remove columns)
#- click+drag: switch time + select frame of the current layer (scribble)
#- shift+click: select column
#- shift+click+drag: selection multiple columns
# Vertical header
#- click: select layer
#- rclick: menu (add/remove layer, show/hide layer)
# Frames Table: empty area.
#- click: select single frame + switch time + *don't* switch layer
#- rclick: menu (insert/copy frame)
#- click+drag: select multiple frames + switch time to the latest + *don't* switch layer
# Frames Table: area on existent frame.
#- click: select single frame + switch time + *don't* switch layer
#- rclick: menu (remove frame)
#- click+drag: *move* a frame or multiple frames
#- ctrl + click+drag: *copy* a frame or multiple frames
#- alt + click+drag: shift the frame and all its right-hand-side frames to the right (stretch the previous frame)
#- shift+click: select column
#- shift+click+drag: selection multiple columns