Problem

The option to edit a field "in-line" (without editing the whole issue) in Jira does not work for all fields or is available only for some fields.

Cause

It is not possible to inline edit those fields that are not added to the Edit Issue screen for the screen scheme associated with the Project/Issue Type.  You'll need to go to your Project Administration and edit your screen scheme to ensure this is in place. 

Resolution

Add the required fields to the screen associated with the Edit Issue operation in the respective screen scheme.  Check out Project screens, schemes and fields for details on how to accomplish this.