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Splunk's operational intelligence platform helps unearth intelligent insights from machine data.
What format is the inputs and outputs of your project management? What is the data like--- qualitative or quantitative? And if it's qualitative, how could you convert the qualitative data into quantitative data for visualization? If there are data in table format, it is very simple to visualize this; even with multiple variables. Thinking what makes a big impact are Sankey diagrams where you see inputs and...
LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
Otherwise, you may be thinking about a "mind-map" of sorts... Simply to show relationships? Diagrams.net, lucidchart.com.