How to create a process flowchart with document links embedded in SharePoint Online Classic

We would like to create process flowcharts that

• link to related process flowcharts
• have links to documents hosted in document libraries
• easy to create and update
• doesn't require developer coding

In the past, members of the team used something call iGrafx, and would like to mimic that functionality in SharePoint Online classic.

Help would be appreciated.

Tutorials would be appreciated.

Examples would be appreciated.

Thanks and have a great weekend.