In Classic Clarity Timesheet some resources see the Add Other Time button while others do not.
Component : CLARITY TIME MANAGEMENT
This depends on if the resource is allocated (on the team) of a NPIO and if the NPIO is active and open for time entry.
If the resource is allocated to a NPIO (Idea, Other Work, Application, Service, etc)
and the NPIO is active and open for time entry and track mode is PPM, the resource will see the button on the timesheet in Classic Clarity.