This answer selects Universal Process Notation (UPN) as the diagramming notation that the BA should use for the process map. UPN is a simple and standardized way of creating process maps, using only four symbols:
activity, decision, start/end, and annotation. UPN can help the BA create a process map that is applicable across all industries, provides context for metrics and management decisions, and supports regulatory considerations. References:
https://trailhead.salesforce.com/en/content/learn/modules/salesforce-business-analyst-quick-look/use-process-ma