Hi @Dirk Nelke,
Welcome to the Microsoft Q&A forum. Thank you for reaching out to us.
When you collapse the Inbox in the new Outlook, the subfolders you recently used may still appear. Could you please check if this issue also occurs when using Outlook on the web?
At the same time, please try clearing the cache and verify if the problem persists. Here are the steps:
Step 1: Close Outlook
Step 2: Press Windows + R, then enter the path: olk.exe --devtools
Step 3: In the tool panel, select Application
Step 4: Under Local Storage, go to Cookies, right-click outlook.office.com, and select Clear
Step 5: Restart Outlook
I sincerely look forward to your response and truly appreciate your support.
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