I have a custom Process Template inherited from the Agile Process Template. By my count, there are 160 Fields available. I plan to directly use about 18 of them. I understand there are several more that are integrated into the system such that they must remain (e.g., Created Date). There are many that I can't imagine are necessary, and that I have no plans to use (e.g. Optional Attendee 1-8). I'd like to completely remove visibility to all those unnecessary Fields so that I don't have to dig through them when making Queries or adding Fields to a Work Item Type's layout. It seems you can only deal with Fields at the all Processes level, and the ability to delete the system ones are all disabled. Is there some other way to mark fields as hidden for certain Process templates?
UPDATE
A feature request has been made for this issue. If you have this same problem, please go vote for it here.
I am afraid that we cannot remove the built-in fields and since they are shared across processes on organizational level, we are unable to limit the field visibilities to specific process or template, when editing a work item type.
For this, you may consider creating a feature request via: https://developercommunity.visualstudio.com/report?space=21&entry=suggestion. That will allow you to directly interact with the appropriate Product Group, and make it more convenient for the product group to collect and categorize your suggestions.