Actually, in 2020 R3 (10.09.000.91) there is no tool to annotate a speed diagram on profile.

I can suggest the following workaround:

• Create a cant for purpose. Give a name such as Cant For Speed Diagram
  Use Force Positive. It is to  get good diagram when using negative cant
  
• Only keep points that are matching speed points
• Set value to get the good diagram
  
• In the profile annotation group set an alias of cant type and define your annotation style for this cant
  It will be the speed
  Note that you must also set an alias for the normal cant. The [Active Cant] setting is not currently reliable.
• When using this annotation group, you will be prompted to select the cant