Modify my limit price - in brief

You cannot modify a current order's price as it stands. Why not?

You can achieve a modification of a limit price by cancelling and re-entering at a different price.

The procedure

Step 1.
more detail

Bring up your orders from the HISTORY ORDERS screen. Select your order and KILL it.

Step 2.
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Click the BUY , SELL , or WIZARD tabs and enter your replacement as appropriate.