No, it's not possible to create a new retainer using your existing plastic retainer.
Creating retainers involves a specific process using a casted mold, which is crafted from the impression you create with the provided putty. Attempting to press your retainer into the putty for an impression would result in an ill-fitting retainer, as it would be disproportionately large for your teeth.
To ensure the production of an accurate retainer, it's essential to adhere to the correct process by creating a new impression of your teeth using the kit provided. This way, we can follow the appropriate procedures to produce a well-fitting retainer.