Go to Setup and search for User Interface. You can also go through the path of Platform Tools > User Interface > User Interface or Build/App Setup > Customize > User Interface (last option). Select Enable Inline Editing and Enable Enhanced Lists then Save.

Why is my inline edit disabled Salesforce?

Known Salesforce Issue (reported bug): The Inline Editing feature may be disabled for List Views when there are more than five (5) Lines of Filter Criteria or when you add Filter Logic. Reduce your Filter Criteria and/or remove Filter Logic, save your List View and try Inline Editing again.

What is inline editing in Salesforce lightning?

Inline editing is a feature by which we can edit a record without pressing the edit button. We can go to the detail page, doubles click on a field, changes to a new value and click on Save and field value is updated to the new value.