I sent a ticket on Technical Paypal Support and received a response regarding this issue. Quoted from part of the email that I received According to your description, you want to dynamically set the free trial in a plan which has be created, right? But unfortunately, our current subscription payment product doesn't support dynamically change the trial info after the plan has been created. So as my suggestion, currently the best solution is to prepare 2 version (trial on/off) for each plan, totally 12 plans, which you have mentioned as well. That's the only method to fulfill your business requirement. In short, there's no way at this current time to have a plan that dynamically change the trial info after the plan has been created.
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