Hello MichalRama,
To delete a task in Microsoft Teams, you can select the task you want to delete, then choose More options and select Delete. However, disabling the creation of a task without assigning it to at least one person in Microsoft Teams is not yet available in Teams.
Source: https://support.microsoft.com/en-us/office/dele...
You can submit your feedback through the portal if this option is still not available so that the Teams Engineer can look into it and add it later.
https://feedbackportal.microsoft.com/feedback/f...
Kind regards,
Jayzar
Please be aware that I am not associated with Microsoft and do not own access to your account. Additionally, I assist other people in our community.