How to add double headed arrows + text

[Ofnuts]

You can:

• define the shaft of the arrow as a path
  
• use my path-arrow-heads script to add arrow heads to it
  
• use my ofn-text-along-path to create text that follows the shaft
  
• Edit>Stroke the path (or make a selection and bucket-fill)
  

... it it looks lore like a job for a schema drawing program (LibreOffice Draw, or else....)