To access the Field Calculator, follow the path:
Management > Field Calculator
On the main page, you will find the list of already configured operations (empty until you create your first operation).
Adding a new operation
To add a new operation, click the button in the top right corner.
First, choose the Field to enhance, which is the database field where the result of the operation will be saved.
The corresponding dropdown menu contains the list of all existing fields in all databases.
For each of them, the belonging database, the field name, and its type are listed.
Once the field selection is made, click Save in the top right corner of the page.
Field Calculator allows operations on all types of fields except for multi-select value lists and simple relationship fields, as well as many-to-many relationships.