Transformations: support a rows mode in labels to fields (#41020)

docs/sources/panels/transformations/types-options.md

@@ -192,20 +192,33 @@ In the example below, I added two fields together and named them Sum.
 
 ## Labels to fields
 
-This transformation changes time series results that include labels or tags into to a table structure where each label becomes its own field.
+This transformation changes time series results that include labels or tags into to a table structure where each label keys and values
+are included in the table result. The labels can be displayed either as columns or as row values.
 
 Given a query result of two time series:
 
 - Series 1: labels Server=Server A, Datacenter=EU
 - Series 2: labels Server=Server B, Datacenter=EU
 
-This would result in a table like this:
+In "Columns" mode, the result looks like this:
 
 | Time                | Server   | Datacenter | Value |
 | ------------------- | -------- | ---------- | ----- |
 | 2020-07-07 11:34:20 | Server A | EU         | 1     |
 | 2020-07-07 11:34:20 | Server B | EU         | 2     |
 
+In "Rows" mode, the result has a table for each series and show each label value like this:
+
+| label      | value    |
+| ---------- | -------- |
+| Server     | Server A |
+| Datacenter | EU       |
+
+| label      | value    |
+| ---------- | -------- |
+| Server     | Server B |
+| Datacenter | EU       |
+
 ### Value field name
 
 If you selected Server as the **Value field name**, then you would get one field for every value of the Server label.