How to change the additional fee to use percentage by Alipay

Hi, I want to set the Alipay, but I find I can't change the additional fee to use percentage, only change it to number, I want to set it just like Paypal, how can I do? Thanks

It does not look like it supports it.  If you're a developer, you can modify the code provided (copy GetAdditionalHandlingFee code from other plugin like PayPal).  If you're not a developer, consider Payment Director.  The Fee Expression would be

  OrderTotalWithoutPaymentFee * 0.03

Where, for example, 0.03 is 3%