Where do support tokens placed by a Door or other terrain come from, and can they move later?

Question

Accepted Answer

From the general supply of unused tokens, never from a marine's own tokens, so activating terrain costs a marine nothing. The tokens stay on the marine or terrain they were placed on until spent or lost, and only a card effect moves them.

Space Hulk: Death Angel – The Card Game

Where do support tokens placed by a Door or other terrain come from, and can they move later?