One of the easiest locations to check yourself is to detect if the field is used in layouts, however, this would be true only when we do not take into account related lists.
You can see the Layouts node with the following details:
- In the 'Object view', 'Layouts' will be present as child nodes for corresponding objects,
- Inside the 'Layouts' node you will find a list of Layouts where your field is used,
- Each layout in the list contains the following sub-items:
- Name of the section, where the field is used on the selected layout,
- Layout Related Lists item, that shows you that the field is included as a displayed column into a related list on the selected layout.
In this section:
This also may be useful: