As per this document, I have added timeline, stopped, stopped since fields in case layout. I am able to see timeline field in classic but not in lightning. As the document state it's available for both. Any idea what am I missing?
There is no timeline field for lightning experience. The other options for this are using lightning app builder- add milestone component to the page. It is not exactly similar to how timeline looks in classic but gives the same information.
Keep the following things in mind when working with case milestones in Lightning Experience. • The Milestone Name and Entitlement Process fields aren’t displayed in Lightning Experience. In Salesforce Classic, these fields appear by default on the case milestone record page. • The case milestones related list isn’t supported in Lightning Experience