Github recently released their PR Templates: https://github.com/blog/2111-issue-and-pull-request-templates. This is a slightly modified version of the one found here: https://quickleft.com/blog/pull-request-template-bookmarklet/ to work with Stash

Stash PR Template.js

// Compressed version
javascript:(function() {var e = document.getElementById("pull-request-description");if (e) {var newValue = "## What does this PR do?\n\nPlease describe what this Pull Request provides.\n\n## Screenshots (if appropriate)\n\nPlease provide a screenshot of the changes made in this PR\n\n## Jira ticket(s)\n\nProvide a list of all affected tickets in this PR\n\n## Related Documentation Updates\n\nIf you updated documentation, please add that here for peer review. Consider using `> ` in front of any change such that it formats well\n\n## Commit History\n\n```\n";e.value = newValue + e.value + "\n```\n";}})();


// Uncompressed version
/*
 * There are slight changes made to the code in the uncompressd version simply
 * to make things a bit more readable when editing the script. All necessary
 * changes will be in the compressed version, so the changes below can largely
 * be ignored as they are strictly for development purposes.
 */
javascript:(function() {
  var e = document.getElementById("pull-request-description");
  if (e) {
    var newValue = "## What does this PR do?\n\n";
    newValue += "Please describe what this Pull Request provides.\n\n";
    newValue += "## Screenshots (if appropriate)\n\n";
    newValue += "Please provide a screenshot of the changes made in this PR\n\n";
    newValue += "## Jira ticket(s)\n\nProvide a list of all affected tickets in this PR\n\n";
    newValue += "## Related Documentation Updates\n\n";
    newValue += "If you updated documentation, please add that here for peer review. Consider using `> ` in front of any change such that it formats well\n\n";
    newValue += "## Commit History\n\n";
    newValue += "```\n";
    e.value = newValue + e.value + "\n```\n";
  }
})();