Consider using pyqtgraph

https://www.pyqtgraph.org/

May be used to replace Matplotlib for the "interactive" GUI stuff, like simulation results and resource plots.

added SFG GUI Scheduling GUI Simulation results GUI labels

mentioned in issue #314

It seems like pyqtgraph has a flowchart module https://www.pyqtgraph.org/images/flowchart.png

I currently looks quite similar to what we have (ugly directly connecting lines etc), but may still be easier/better to adapt it in the long run. It seems like it is possible to "simulate" within the flowchart, but "One major limitation of flowcharts is that there is no mechanism for looping within a flowchart.".