Any order that hasn't executed yet (a resting Limit order, a Trigger order, or a TP/SL attached to a position) can be modified or cancelled from the Open Orders tab.
Modifying lets you adjust an order's trigger or limit price without losing your place; cancelling removes it entirely.
Cancelling Orders
Go to the Open Orders tab.
Find the order you want to remove and press the X icon on the right-hand side.
Press Confirm to complete the cancellation.
The order is removed immediately and will no longer execute. Keep in mind that cancelling a TP/SL leaves your underlying position open and unprotected - the position stays live, but no longer has a take profit or stop loss attached.
Modifying Orders
Go to the Open Orders tab.
Press the pencil icon next to Trigger on the order you want to change.
Edit your Limit order or TP/SL trigger price.
Press Confirm to save your changes.
Modifying updates the price on the existing order rather than replacing it, so the rest of the order's settings stay as they were. This is the quickest way to move a stop loss or adjust a limit price as the market moves, without having to cancel and re-enter.
Things to keep in mind
Only orders that haven't filled yet appear in Open Orders. Once an order executes, it's no longer editable.
A trigger or TP/SL order fires based on price conditions, so changing the trigger price changes the level at which it will execute — double-check the direction before confirming.