Alert: How to format timestamp in Notification message

1. Describe your incident:
I want to format the timestamp in the Notification message.

Following:
<tr><td>Timestamp</td><td>${message.timestamp}</td></tr>

Results in:
Timestamp 2024-12-19T16:54:33.835+01:00

I want to have it like:
Timestamp 2024-12-19 16:54:33

There was a similar request in the community, but without an answer:

2. Describe your environment:

  • Graylog Open 6.1.2

3. What steps have you already taken to try and solve the problem?
${message.timestamp;format_date(“YYYY-MM-dd HH:mm.ss”)}

4. How can the community help?
Can I use this ‘format_date(…)’ function? And how?