TOC structure from CPT 2019 not shown in ALMS (no folders or levels)

Hi, I've created a training in CPT Classic (2019) with a structured TOC. The slides are distributed over different folders. That is exactly what I want: The folders give a structure, and the slide entries allow for easy navigation.
However, when transferring this to the ALMS, the TOC structure seems to get lost: It is reduced to just one level. 
- When keeping the folders in the CPT, the folders are displayed in the ALMS, but can neither be opened nor can the users navigate with them. The slide TOC entries are not shown at all. 
- When deleting the folders from the CPT, the slide TOC entries are shown in the ALMS and allow for navigation. However, they are not structured and thus look somewhat chaotic. 
=> What do I have to do for presenting my clients professional TOCs in trainings via ALMS?
Thanks!