Problem:

I have some post forms to edit existing content and I need a way to either hold the edits the user has made until they're reviewed

Solution:

There isn't such kind of built-in feature, the editing post form will override the custom field values, so the original field value will lost after user submit the editing post form.

As a workaround, you might consider these:

https://toolset.com/forums/topic/send-form-notification-with-only-fields-that-were-changed/#post-2273811

Relevant Documentation:

https://toolset.com/course-lesson/selecting-parent-posts-when-using-forms-to-create-child-items/

Problem:

Get some PHP errors when using PHP 8：

https://toolset.com/forums/topic/migrated-to-a-new-server-but-archive-pages-are-now-blank-useragent-error/#post-2273923

Solution:

PHP 8 is currently not supported due to some issues:
https://toolset.com/toolset-requirements/

Please downgrade to PHP 7.4, and test again

Relevant Documentation: