How can I automate adding Request Participants using JSM and Assets?

The reporter will tell you who the person is who emailed the request. 

1. Use the reporter's email address to find the people asset:

Within a lookup objects, do something like "Email attribute name" = {{reporter.emailAddress}}

2. you have a {{lookupObjects}} smart value available to you to use, drill down to the location and the location's manager:

{{lookupObjects.Location attribute name.Manager attribute name}}

3. If that Manager attribute name is a Jira user, you can use the above to directly populate the Request participants field, if it is an asset, you can use the email address on the asset to find the Jira user (either if it is a property on your asset OR use the REST API otherwise)

Note if you want to keep any existing request participants, do {{issue.Request Participants}} {{lookupObjects.Location attribute name.Manager attribute name}} - assuming the manager attribute name is a Jira user attribute type, otherwise use something else as described above in #3

Let me know if you have questions on the above, thanks!

@Lenny Thaw 

Welcome to the community.

I agreed with @Andrea Robbins suggestion.  In addition, once when you test out the capture of the needed users to the specific JSM requests, then you can adjust your automation rule to conduct an action using "Send Mail" where you can create your custom email notification to them.  

Your rule may be also require the different conditions on the # of days action.

Hope this also helps.

Best, Joseph