Break the functionality of the product into a set of functional requirements, at higher level (from the customer perspective), by using User Stories. Reading the set of high-level functional requirements is expected to give a clear understanding of what the system will allow its users to do. This set of requirements is structured in a logical manner. For example, if you list 20 functional requirements, it is expected that they are organized into a few groups in a logical manner. Also, it is expected that there is some logic behind the order in which the functional requirements are listed. Use the Wiki section (of Gitlab, for example) to define them.
Prioritize the requirements as must-have, should-have, could-have, or won't-have.
"Functional requirements - High level" should be written as a separate entry in the Wiki.
