It is not possible to open leverage operations in opposite directions for one tokenised asset within the same wallet (opening a long-operation when you have a short-operation open, or vice versa; also known as hedging mode) on Currency.com. If you open such a leverage operation, the previous operation will be edited in volume or closed.
You also receive a relevant notification when trying to open differently directed operations:
If the volume of the new leverage operation is less than the volume of the active one, the volume of the active operation will decrease, and a new leverage operation won't be open.
Since this information is only relevant for operations opened within the same wallet, you can use two different wallets to open leverage operations in different directions (e.g. USD.cx for long-operations and EUR.cx for short-operations).