As far as I know, You can only use the function sort() to sort metrics by value.

• According to this PR, Prometheus does not intend to provide the function sort_by_label().
• According to this Issue, Grafana displays the query results from Prometheus without sorting.
• According to this Issue, Grafana supports sorting by value when displaying legend.

In Grafana 7, Prometheus metrics can be transformed from time series format to table format using the Transform module, so that you can sort the metrics by any label or value.

In December 2023, prometheus v2.49 finally added sort_by_label() and sort_by_label_desc()

We can use query_result to achieve this. https://grafana.com/docs/grafana/latest/datasources/prometheus/template-variables/#use-query-variables

query_result(topk(10, sort_desc(sum(http_tt_ms_count) by (api_path))))

http_tt_ms_count - is my metric timeseries of Prometheus with time taken.

api_path - is my label name

This query_result will give three-tuple value like this.

{api_path="/search/query"} 25704195 1507641522000

used the Regex field in query path to get only the api names.

*api_path="(.*)".*

This looks like a long way but

label_values((topk(10, sort_desc(sum(http_tt_ms_count) by (api_path)))), api_path) 

is not working in Grafana which made me to go into this path.

Try using sort_by_label function from VictoriaMetrics (I'm the author of this Prometheus-like system) in the following way:

sort_by_label({__name__=~"foo|bar|baz"}, "__name__")

It should sort the returned time series by their metric names.

If you need to sort time series with idenrical metric names by their value, then try the following MetricsQL query:

sort_by_label(
  sort({__name__=~"foo|bar|baz"}),
  "__name__"
)

It uses an additional function - sort - for sorting time series by values, before sorting time series by metric names.