Diagram support

You can use plantuml, flowchart or Sequence as a diagram describing tool.

plantuml

@startuml
actor actor
agent agent
artifact artifact
boundary boundary
card card
cloud cloud
component component
control control
database database
entity entity
file file
folder folder
frame frame
interface  interface
node node
package package
queue queue
stack stack
rectangle rectangle
storage storage
usecase usecase
@enduml

See: http://plantuml.com

flowchart

Please remove back slashes \ before `

\`\`\`flowchart
st=>start: Start:>http://www.google.com[blank]
e=>end:>http://www.google.com
op1=>operation: My Operation
sub1=>subroutine: My Subroutine
cond=>condition: Yes
or No?:>http://www.google.com
io=>inputoutput: catch something...

st->op1->cond
cond(yes)->io->e
cond(no)->sub1(right)->op1
\`\`\`

Sequence

\`\`\`sequence
Title: Here is a title
A->B: Normal line
B-->C: Dashed line
C->>D: Open arrow
D-->>A: Dashed open arrow
\`\`\`

ref

https://github.com/BoostIO/Boostnote/issues/771#issuecomment-322023940