Extract a substring from field name

Hi community,
I am still learning Grafana, but now I faced a problem I can not solve alone.
I am using Grafana v9.1.6 with Zabbix plugin. (Zabbix version is 6.0)
I would like to create a panel, where I could check the total space of each disk that my Linux host has. I would like to see everything in one panel, which is why I chose Bar gauge as visualization.
I would like to extract a substring from the field name, but I have had no success so far.
Here is what I have now:

I would like to manage somehow to show only the disk name without the Hostname and “Total space”. So the final should be like " / , /boot, /srv/nfsdata".
I followed this (I want to remove a string from the legend format in Grafana - #2 by melori.arellano) link but it is still not working. I set up Value mappings, I don’t get any error messages, it looks like the regex is just not taking any effect.

The raw data column headers look like this:

  • Time
  • K8sData: /: Total space
  • K8sData: /boot: Total space
  • K8sData: /srv/nfsdata: Total space

Can you please give me some hints on how I could manage what I want?
Thank you in advance.

  • What Grafana version and what operating system are you using?

  • What are you trying to achieve?

  • How are you trying to achieve it?

  • What happened?

  • What did you expect to happen?

  • Can you copy/paste the configuration(s) that you are having problems with?

  • Did you receive any errors in the Grafana UI or in related logs? If so, please tell us exactly what they were.

  • Did you follow any online instructions? If so, what is the URL?