Unable to combine the legend expression with the plain text together in Legend

  • What Grafana version and what operating system are you using?
    7.5.1 version and Win10

  • What are you trying to achieve?
    I want to put a plain text and legend expression together in Legend, for example, I have below metrics query:
    avg(node_filesystem_size_bytes{instance=~"${end}",device=~"${fs_device}",fstype=~“xfs|ext.*”})by(device,instance)

And I use {{fs_device}} in Legend, it is presenting as below:
{device="/dev/mapper/rootvg-lv_root", instance=“192.168.12.126:9100”} Current: 97.5 GiB

But when I add “Total space” ahead of {{fs_device}}, it will no longer showing {device="/dev/mapper/rootvg-lv_root", instance=“192.168.12.126:9100”} any more, but only showing Total space.

What I want to achieve is to show something like below as Legend:
Total space: {device="/dev/mapper/rootvg-lv_root", instance=“192.168.12.126:9100”}

My variable:
fs_device:
label_values(node_filesystem_size_bytes{instance=~"$end"},device)
end:
label_values(node_uname_info,instance)