Hi Matt,
You got it correct. That leads you to Task Definition (sc_ic_task_defn) table. The problem which you have encountered is because the fields are set as Read Only from their dictionary as part of OOB definition. But as part of project requirment you always (or conditionally) can make the fields editable.
Here I am providing you the solution to make the fields non-editable. Please follow this link (https://your_instance.service-now.com/sys_dictionary_list.do?sysparm_query=name%3Dsc_ic_task_defn%5EelementINsc_cat_item%2Corder%2Cactive%2Cshort_description%2Cdescription%2Cassignment_type%2Cassignment_group%2Cassignment_user%2C). You need to provide your instance name in the above URL for proper navigation. You will be redirected to the Dictionary level of all those fields which you want to make editable. Then you need to bring the 'Read only' column in the list view by using 'gear icon'. Post which you always can modify them to True and achieve what you are looking for. Similarly you can modify other fields also, if necessary. Refer the below image.
Hope this helps. Please mark the answer Correct/Helpful based on impact.
Regards,
Amlan
