How to setup matching rule where user can do manual match within source system for BC Match Type

We have BC Match type where we have Source and sub system.

We have existing setup where we have setup Auto match, Suggested match and manual match rules for source and sub system.

We got new requirement from the business where they want to match transactions within source system. We explored the option and could not add rule to match debit credit entry within source system with existing setup.

We created new matching process within existing match type to only match source to source transactions but now we have to change match process in rec to actually use the newly created match process and which is making process more complex.