How to add fields to BP (not hardcode)?

Question

1C-Bitrix

Good day everyone. Please tell me how to be.
I am doing a business process for a client to agree on various payments.
Of course, when paying bills, there are deferrals and fractional payments (up to 5 pcs per 1 account).
How can you implement the functionality of adding fields that will contain information about the surcharge without creating these fields in advance?
Example:
By default I have 3 fields -

1. counterparty
   
2. payment date
   
3. Payment amount
   

A week later, an additional payment may be made and information about it must be added to this BP.
Is it possible not to hardcode these fields (2 per surcharge) by default so that they do not interfere with working with clients who do not have surcharges?