After choosing the target (if applicable), the Cargo Transfer window displays the unit you started with on the left, and the target on the right.

  • ↑, ↓: Choose kind of cargo to transfer;
  • ←, →: Move 10 units;
  • Shift‐←, Shift‐→: Move 1 unit;
  • Ctrl‐←, Ctrl‐→: Move 100 units;
  • Alt‐←, Alt‐→: Move as much as possible;
  • U: If one unit is a planet, unload all T/D/M/$/Sup/Colonists to it;
  • S: If one unit is a planet, toggle automatic supply sale. Supplies you move off one unit appear as megacredits on the other;
  • Enter: Confirm. Execute the transfer and close the window;
  • ESC: Cancel.

Reference

Keys:
C and U from control screens;
See also:
Sell Supplies.