PSE 2020 Album Hierarchy Set Up

How do I set up sub-albums in PSE 2020? I’ve been trying to set up an album structure, but I keep getting stuck. Months and years ago, I imported my photos into monthly folders in Photoshop (it was 5.0 at the time), and now I want to set up a hierarchy of albums to populate from my Photoshop 2020 folders.

The Categories and Albums I want to set up are:

        My Albums

                Cruises

                        Baltic Cruise August 2018

                                8/18-8/19 SF-Stockholm

                                8/20 Tallin, Estonia

                                8/21 St. Petersburg

                                Etc.

I can set up the category “Cruises” and add the album “Baltic Cruise” under it, but if I try to add a sub-album under that, the only available options under “New Album” are  “None - Top Level” and “Category - Cruises”. I don’t get an option to add a sub-album, such as “8/18-8/19 SF-Stockholm” under “Baltic Cruise”. I have spent a lot of time reading various help screens and Adobe Community discussions but haven’t yet found an answer. What am I missing?

Thanks!