I'm afraid you can't. Even if you buy Scriptdio PRO without the Standard Version, you will not be able to log in.
Here is why:
1. Scriptdio Standard is the main product which is either a Monthly, Yearly, or One-Time Subscription.
2. Scriptdio PRO is an Upgrade or Upsell which adds the PRO features to your Scriptdio account.
3. Since Scriptdio PRO is not independent, you will need to subscribe for the main product Scriptdio Monthly, Yearly, or One-Time subscription first. Else you can't log in with only Scriptdio PRO in your account.