All users, except for collaborators, can see the Custom Field History in folder and project info panels unless their access role restricts it.
Custom Field History shows how custom field values in tasks, folders, and projects change over time. The history records each time a user edits data in the custom field of a folder or a project.
Open the Task view or a folder/project info panel.
If you don't see custom fields, click the square icon in the toolbar at the top of the window to expand them.
Hover over a custom field.
Click the clock icon.
In the overlaying window that opens, you will see:
All values that were entered in the field. They appear in chronological order with older values closer to the top.
The name of the user who entered a value.
The date of the change.