Dear Claire_070,
Thanks for reaching out to us here in Microsoft Community.
After reading, I have a general idea of your problem.
When you try to snooze an email thread, you actually snooze all emails in the thread at the same time. This is the design.
I have a suggestion for you:
If you want to snooze a single email, you can change the view settings: click View - Conversations - Show each message seperately, then all the emails in a thread will be displayed in your list, and you can choose to snooze the most recent one, which not only ensures that when the single email returns to your inbox, only one email will be counted, but also ensures that you can view the entire thread.

Of course, after performing the snooze operation, you can also change the setting back to Group Into Conversations, If you feel that displaying each email individually will make your email list too cluttered.
I know this will work but it's still a bit cumbersome. Sorry any inconvenience, if you want to share this issue with the development team, you can also choose Feedback from the Help tab of the Outlook ribbon to report this problem or click this link Outlook · Community
I hope my suggestions are helpful to you.
Feel free to contact me if you have any questions, I am here to help you further if needed.
Best Wishes,
Stan - MSFT | Microsoft Community Support Specialist