Jellyfin Webhooks supports custom helper methods like {{#if_equals <a> <b>}} and {{#if_exists <a>}}.
These can be used in the template to exclude certain values if the notification has or lacks some properties.

What I'm missing is a logical && and/or || operator that can be used to exclude entire sections based on multiple conditions.

Example:
I have this template which only makes sense for events caused by playback (Start, End, Progress):

  "Playback":
  {
    "PlaybackPosition": "{{PlaybackPosition}}",
    "TotalRuntime": "{{RunTime}}"
  }

To get this data to show for all of these events, but none other, I have these options:

1. Just let the section always show up for all webhooks
2. Add the following:

{{#if_equals NotificationType 'PlaybackStart'}}
  "Playback":
  {
    "PlaybackPosition": "{{PlaybackPosition}}",
    "TotalRuntime": "{{RunTime}}"
  }
{{/if_equals}}
{{#if_equals NotificationType 'PlaybackEnd'}}
  "Playback":
  {
    "PlaybackPosition": "{{PlaybackPosition}}",
    "TotalRuntime": "{{RunTime}}"
  }
{{/if_equals}}
{{#if_equals NotificationType 'PlaybackProgress'}}
  "Playback":
  {
    "PlaybackPosition": "{{PlaybackPosition}}",
    "TotalRuntime": "{{RunTime}}"
  }
{{/if_equals}}

For purposes like this, it would be preferable if there were some kind of logical operators available, e.g.:

{{#if_any NotificationType 'PlaybackStart' 'PlaybackEnd' 'PlaybackProgress'}}
  "Playback":
  {
    "PlaybackPosition": "{{PlaybackPosition}}",
    "TotalRuntime": "{{RunTime}}"
  }
{{/if_equals}}

Or similar.

Now, I'm quite familiar with .NET, but have never squabbled with Handlebars.NET, so I don't know how hard this would be, or if it would be easier to implement logical OR/AND operators instead ({{#if_equals NotificationType 'ProgressStart' || 'ProgressEnd' }}, but a feature like this would make the templating much more compact in certain scenarios.