In the old interface, when adding a physical edition of a book, you can check "Other formats and editions" in the right-hand side panel.
Existing editions are separated into "Electronic versions" and "Other editions".

However, in the new UI, both electronic and physical editions are mixed and presented in one single list. If there are many editions of a book and the instructor is only looking to add an electronic version to a citation, then the many editions make it hard to quickly identify the few electronic versions.

The list would be more readable if electronic and physical formats were presented in separate categories.