{{issue.components.name}}
{{issue.created.format("dd/MM/yyyy")}} - this is the date the issue was created
displayed in the format 21/03/2019
{{issue.description}} - the content in the description field
{{issue.project}} - the project this issue is a part of.
{{issue.duedate}} - this is the due date for scheduled issue
{{issue.issuetype.name}} - the name of the type of issue
{{issue.key}} - the issue's unique identifier, comprised the project key and the
issue's number
{{issue.status.name}} - the name of the status the issue is at in its workflow.
{{issue.toUrl}} - use this to display a url
{{issue.CustomField.property}} - some of these are:
  * {{issue.CustomField.id}} - the unique id for the field assigned by Jira. It is
    better to use this than name as it cannot be changed.
  * {{issue.CustomField.name}} - the visible label displayed on the left of the
    field
  * {{issue.CustomField.description}} - the text displayed below the custom field
    viewed in the Simple Search column.
  * {{issue.CustomField.defaultValue}} - the value displayed on first view of the
    field

{{#issues}}{{key}}{{/}} - the key for each issue
{{issues.size}} - count of the issues

{{#issue.comments}}
Comment by: {{author}} at: {{created}}
{{body}}
{{/}}

{{issue.comments.last.body}}
{{issue.comments.first.body}} - the body of the first of many comments
{{issue.comments.size}} - count of comments for the issue

{{#issue.comments}}{{#first}}First:{{author.key}}{{/}}{{body}}{{/}} - prints all of the comments and only prints the first author's key

{{issue.components.first.name}}

{{issue.epic.key}}
{{issue.epic.status.name}}
{{issue.epic.My Custom Field}}

{{issue.fixVersions.first.releaseDate}}

{{issue.latest.description}}

{{issue.parent.key}}
{{issue.parent.priority.name}}
{{issue.parent.Epic Link}}
{{issue.parent.epic.summary}}

{{issue.properties.some.value}}

{{issue.project.key}}
{{issue.project.name}}

{{issue.Request Type}}
{{issue.Request Type.requestType.name}} - Customer request type
{{issue.Request Type.currentStatus.status}} - Current  status
{{issue.Customer Request Type}} - Customer request type for older Jira instances

{{issue.security.name}}
{{issue.security.id}}

{{issue.url}}
{{issue.url.customer}}

{{issue.versions.first.releaseDate}}

{{issue.watchers.displayName}}
{{issue.watchers.emailAddress}}

These are the issue keys found by the JQL search {{lookupIssues.key}}.

These are the issue keys found by the JQL search:
{{#lookupIssues}}
* {{key}}
{{/}}

There are {{lookupIssues.Story Points.sum}} story points remaining.

The highest story point value is {{lookupIssues.Story Points.max}}.

{{triggerIssue.description}}

{{attachment.filename}}             // Provides the filename of each attachment
{{attachment.mimeType}}             // Provides the file format of each attachment
{{attachment.author}}               // Provides the user who added each attachment
{{attachment.author.accountId}}     // Provides the ID associated with the user who added each attachment
{{attachment.author.emailAddress}}  // Provides the email address associated with the user who added each attachment
{{attachment.author.displayName}}   // Provides the display name associated with the user who added each attachment
{{attachment.author.active}}        // Provides the status (active/inactive) of the user who added each attachment
{{attachment.author.timeZone}}      // Provides the timezone of what timezone of the user who added each attachment
{{attachment.created}}              // Provides the date and time each attachment was added to the issue
{{attachment.size}}                 // Provides the size in bytes of each attachment

{{#attachment}}
[^{{filename}}]
{{/}}

{{#attachment}}
!{{filename}}|thumbnail!
{{/}}

{{#changelog.summary}}
  {{toString}}
{{/}}
{{#changelog.issuetype}}
  {{fromString}}
{{/}}
// Previous status name
{{#changelog.status}}{{fromString}}{{/}}
// Previous status id (for using in another Edit action
{{#changelog.status}}{{from}}{{/}}

{{comment.body}}
{{comment.author}}
{{comment.created}}
{{comment.visibility.type}} - comment restriction type, if any e.g. role
{{comment.visibility.value}} - comment restriction label, if any  e.g. Developers 
{{comment.internal}} - for Jira Service Management comments, returns false if the comment is visible to customers.
{{comment.properties}} - Way to access any comment property. Properties are frequently used by add-ons and integrations to store values.
{{comment.properties."sd.public.comment".internal}}

{{createdIssue.some field}}

{{#createdIssues}}{{key}}{{/}}

{{eventType}}

{{fieldChange.fromString}}  // Returns the previous value as displayed.
{{fieldChange.toString}}    // Returns the new value as displayed.
{{fieldChange.from}}        // Returns the previous raw value of a field, i.e. the JSON representation of the value.
{{fieldChange.to}}          // Returns the new raw value of a field, i.e. the JSON representation of the value.

{{#changelog.fix Version}}{{toString}}{{/changelog.fix Version}}

{{issue.Satisfaction.rate}}

{{issue.Satisfaction.scale}}

{{rule.name}} - Prints out the name of the running rule
{{rule.actor}} - Accesses the rule actor user.

{{sprint.id}}
{{sprint.name}}
{{sprint.isStarted}}
{{sprint.isClosed}}
{{sprint.startDate}}
{{sprint.endDate}}
{{sprint.completeDate}}
{{sprint.originBoardId}}
{{sprint.goal}}

{{version.name}}
{{version.id}}
{{version.description}}
{{version.archived}}
{{version.startDate}}
{{version.released}}
{{version.releaseDate}}
{{version.project.key}}
{{issue.versions.first.name}}

{{webhookData.someValue.childValue}}

{{webhookResponse.status}} - response code e.g. 200
{{webhookResponse.headers}} - headers that can be accessed with dot nation
{{webhookResponse.headers.Content-Type}}
{{webhookResponse.body}} - body that can be accessed with dot nation
{{webhookResponse.body.name}}
{{webhookResponses}} - list of responses made when list operations
{{webhookResponses.last.body}}

{{webhookResponses.last.someValue.childValue}}
{{#webhookResponses}}
    Data from response: {{someValue.childValue}}
{{/}}

{{worklog.comment}}
{{worklog.started}}
{{worklog.timeSpentSeconds}}
// Cloud only
{{worklog.timeSpent}}
// Visibility is available when the worklog is restricted
{{worklog.visibility}}
{{worklog.visibility.type}}
{{worklog.visibility.value}}

{{issue.InsightField}}          // returns Some Client Name (ABC-123)
{{issue.InsightField.key}}      // returns ABC-123
{{issue.InsightField.summary}}  // returns Some Client Name

{{issue.TempoAccountField}}       // Provides the name of the account
{{issue.TempoAccountField.id}}    // Provides the ID of the account
{{issue.TempoAccountField.name}}  // Provides the name of the account
{{issue.TempoAccountField.key}}   // Provides the key of the account