Reply To: Subscription modification
The asterisk in the level attribute is used when selling only the capability, which can only be done with buy-now, not a subscription.
What do you mean by increasing the next payment? You mean in a subscription? Only when it’s a new subscription, you can’t modify an existing one. And you can only set the first payment (initial) or all the following payments to be different (recurring), but not only the 2nd or 3rd payment (these will be the same as all the recurring payments, they can’t be different).
Yes, using 1 in the shortcode, will sell a new subscription, ending an existing one. The user can’t have multiple subscriptions.