In my experience, many end users believe that with perhaps an hour or two of training, they will be able to create their own reports. This is not just an Odoo issue—it is a common perception that many end users have when working with an ERP system. Unfortunately, creating or modifying reports is often not easy and should be considered more of a developer task than an end user task. Be prepared to spend a considerable amount of time acquiring the skills required to make significant changes to the documents and reports in Odoo.
Furthermore, reporting has changed dramatically in the past few years. Previously, many companies were dependent on paper reports and Excel sheets to properly communicate information throughout the company. Very often in Odoo, what was previously a physical report can better be managed through filtering...