Nice article, you should past a link to a gist w/ the json

Great article! Last week I discovered two (advanced?) things that you might be interested in: getting flow variables in subflows and the status message

Getting a flow variable from a subflow

The sun position dictates a flow variable in my lights automations. It sets a brightness modifier so I'm not blinded at night. This is how I format the JSONata for the light.turn_on service call:

{
   "transition": 2,
   "brightness_pct": ( 0.01 * $flowContext('$parent.sun_brightness_modifier') ) * $env('BRIGHTNESS_BASE')
}

Mind the $flowContext('$parent.variable_name') syntax: with $parent you get access to the subflows parent variables.

Outputting a node status for a subflow:

The status node lets you update the message that's underneith the subflow node. Now, my formatting is not very pretty but the information is very useful!

The JSONata for the message formatting:

{
  "fill": "green",
  "shape": "dot",
  "text": $join(['On:', $env('ENTITY_ID'), "at:", $now()], ' ')
}