Custom fields is available only for Essentials and Enterprise+ tiers. Only Admins and those who've edit permissions on a plan can apply custom field template to that plan.
The custom fields are created, grouped into templates, and applied to plans. Capture data with these custom fields and delve deeper into your strategic insights.
The entities in the plan to which the custom fields are applied will display those depending on how you defined them. Let's open the Sidebar view of an objective to which the custom field was applied.
In this template, we've three groups - Effort and Budget with numerical field types, and Priority with dropdown field type. Each of these groups track separate values, as defined earlier in Create Templates and Custom Fields.
No data has been populated against these fields yet. Now, lets start entering data in the Edit Objective Sidebar, by clicking on the 
icon.
The groups are listed - edit them with relevant values, and click Save.
For numerical fields where Allocated and Spent values are defined - the sidebar displays a progress bar to provide a summary visualization of how much is consumed against the total available. However, if the fields have other labels, then the progress bar will not be displayed.
Expand the Effort and Group sections to see all the details, and this'll provide you a visibility of the remaining allocation available to spend or utilize.
If multiple selections are chosen and saved in a dropdown field, those will be displayed alongside that custom field in the Sidebar.
The custom field data captured via the sidebar is static and point-in-time only. There is no record of historical data, updating the value will override the previous value.