cmd: example on modifying any outputs into a plots

content/docs/command-reference/plots/modify.md

@@ -26,6 +26,10 @@ The path to the metrics file `target` is required. It must be listed in a
 `dvc.yaml` file (see the `--plots` option of `dvc run`). `dvc plots modify` adds
 the display properties to `dvc.yaml`.
 
+Convert any
+[output or simple metrics file into a plot](#example-convert-any-output-into-a-plot)
+by passing it as a `target` to `dvc plot modify`.
+
 Property names are passed as [options](#options) to this command (prefixed with
 `--`). These are based on the full
 [Vega specification](https://vega.github.io/vega/docs/specification/).
@@ -131,3 +135,27 @@ be changed in many cases. A simple command changes the template:
 ```dvc
 $ dvc plots modify classes.csv --template confusion
 ```
+
+## Example: Convert any output into a plot
+
+We can use `dvc plots modify` to make an <abbr>output</abbr> or simple metrics
+file of a stage into a plot. Lets take an example `evaluate` stage which has
+`logs.csv` as output. To change the output file `logs.csv` into a plot run:
+
+```dvc
+$ dvc plots modify logs.csv
+```
+
+Changes in `dvc.yaml` shows `logs.csv` is now a plot:
+
+```git
+evaluate:
+  cmd: python src/evaluate.py
+    deps:
+    - src/evaluate.py
+-   outs:
+-   - logs.csv
+    plots:
+    - scores.json
++   - logs.csv
+```