I know I can customise the Slack icon used with the JIRA Automation Slack channel posting - and I'm using it now, on a few automations. I've set the icon that I want in the webhook settings in Slack - great.
What I now want to do is change that icon within the JIRA Automation rule based on IF criteria.
I can see in the webhook notes you can set it in the JSON payload:

However, I cannot see how to incorporate this into the rule in JIRA.
Any ideas?