One way vs Hedge mode

One way mode - allows for one position per instrument on derivative pairs.

Hedge mode - allows for one position on each side per instrument on derivative pairs, meaning you can have one long and one short open simultaneously on the same pair.

You can adjust this mode here within the sidebar:

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note - when in both isolated margin mode & hedge mode together, you toggle the button highlighted below next to your percentage hotkeys to switch the buy margin balance or sell margin balance.