In Lightning Experience, the Send Email feature is a great tool for composing emails that are then tracked and logged as an activity on a record. However, when selecting a file/attachment to include with the email, it is difficult or impossible to find find and select the Files that are attached to the record that the email is related to. It seems like a relatively straightfoward solution to include a filter for files related to the Related Object.
Below is an example of how this could work. The Name of the record is included in the Select File modal and would show Files that are associated with that record: