I can only think of a workaround by doing a dry-run install and then greping for the value.

E.g.

helm install --dry-run jenkins_temp stable/jenkins | grep value_name

From the docs

When you want to test the template rendering, but not actually install anything, you can use helm install --debug --dry-run ./mychart. This will render the templates. But instead of installing the chart, it will return the rendered template to you so you can see the output

or you could fetch the Chart as a tar file.

helm fetch stable/jenkins --untar

less ./jenkins values.yaml