Resolution:
If while creating a new or editing a procedure the TIBCO iProcess Modeler is killed it is possible for the lock on the procedure to be left behind.

There are two tables in the database that can contain procedure locks.
pm_objects_lock
procedure_lock

Delete the entries for the locked procedure in both tables to unlock the procedure for editing.

Example in SQL:

delete procedure_lock where proc_id = (select proc_id from
proc_index where proc_name = ’PROCNAME’)

delete pm_objects_lock where object_guid = (select object_guid from
pm_objects where object_name like ’PROCNAME’)

NB: Care should be taken when deleting rows from the database.

How can you remove the "This procedure is already being edited" message if the TIBCO iProcess Modeler had been in use when a client machine crashed?