This is a graph maker using the Mermaid.js Diagramming and Charting Tool which is a diagramming tool that makes graphs based on Markdown like code. Feel free to mess around with it and consult the syntax at their documentation.
The only thing you need to do in Perchance is to escape the Mermaid syntax (since it also uses [ ] heavily) with backslashes \ so Perchance will not execute them as lists.
Almost all of the types of grouping symbols are used mostly on the flowchat / graph charts since they dictate the shape of the nodes, but on the other graph types, it is not as used. Here is the documentation for reference