Custom Column on Custom Report

I am a relatively new user of Manager and a first-time user of this forum. I thought I should do a thorough search of existing questions/answers before posting one that might be redundant, but did not find a search facility, so I am assuming that the “Your topic is similar to…” facility accomplishes that. I have read the questions/answers suggested and have not found an answer to my question.

A. I have discovered Custom Reports.
B. I have been able to use that report generator method to create a report that is almost what I need.
C. What I need, however, is an additional calculated result column, but, as far as I have been able to use the report generator it only allows selection from data fields held in the internal database.
D. Elsewhere, however, there are mechanisms for the creation of custom fields and calculations in custom themes.

What I cannot find is a means for adding a custom field to a custom report; the explanations seem to limit the use of custom fields to forms.

Click the magnifying glass icon in the upper right corner: 05%20AM

That is correct. Reports (of any kind) only present data already in the database. Custom fields are specific to transaction forms.

Thank you for a quick response. So, is my understanding also correct that there is no way to add a calculated column to a custom report?

Correct. But you can copy it to the clipboard, paste into a spreadsheet, and add calculations there. See https://www.manager.io/guides/18075.