To change rights of who can and who cannot create issues via The Scheduler add-on please follow the below steps:
Please note that to perform the below actions you must be granted with Project Admin rights.
From the "Projects" drop-down menu (1) please select a desired project, in which you plan to amend or add new permissions for a scheduled issues management. After that please scroll down and access "Project Settings" (2).
On a newly loaded page:
Finally you will see:
