After several years, I discovered that my humidifier was supposed to have an aroma tray (according to the attached manual), but it was missing. So, I 3D-printed one and started using it.
Funny fact: in the PDF manual, this tray is absent! https://cooperandhunter.ua/split/files/docs/support_20190320154804523.pdf
The author marked this model as their own original creation.