This is probably the "hard" way, but knowing how the relationships work, you could work backward to find the data you want. 

When you run a Playbook, it creates a record between the source record (A case?) and the playbook definition. That then writes data to the Flow Data table, which in turns stores entries (I'm looking at a questionnaire) in the Variable Value table. 

So here would be the process: 

1. Get the related playbook context record from "sys_pd_context" where input_record = Case sys_id

2. Look up the Activity where the input happened on table "sys_pd_activity" where context = record from #1

3. Look up the sys_flow_data record where sys_id = the "associated_record" id in #2

4. Look up the related variables in sys_variable_value where document_key = the Flow Data record from #3

Added bonus: there are wonderful ways to update the input fields (like on a questionnaire) that don't exist in the UI. For example, you can put advanced reference qualifiers or use attributes like the following by modifying the related sys_flow_data_var entry. 

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