Flow charts are a great way to visualize technical sequences in Brazilian Jiu Jitsu. Wether done by freehand or computer is your choice. The important thing is, that you draw the flow charts yourself. It makes no sense copying the flow chart of a world class BJJ Competitor.
You may build your flow diagram around the basic positions e.g. mount, guard, sidemount or around basic submissions e.g. Kimura, Armbar, Leglock etc.
Another very good way is to visualize submission chains (sequences) as there are many such chains in Brazilian Jiu Jitsu. If one submission fails then very often another submission lays on the way. E.g. if you opt in the closed guard for a Kimura, then either a sweep ore the Guillotine lays on the way.
Flow charts are also perfect to keep in mind the priorities in Brazilian Jiu Jitsu. if you are caught in a closed guard your first priority should be to gain a proper posture. Nothing else matters than this. Only then comes the guard opening. The third step will be your decision conserning guardpass or legattack etc.
So try to build your own flow charts. I am persuaded it will boost your game on the mat.
Below you see an old flow diagramm from Rickson Gracie. And a recent one i draw myself one the topic of the open guard bottom attacks (submission chains).