Hi @Kristen_Sukalac, welcome to the Asana Community Forum!
As it stands, it’s currently not possible to disable project notifications in all projects you are a member of at once. You can see the list of projects you are member under each team in your sidebar but you will need to manage the settings of each project separately. Apologies for any inconvenience and thanks for your feedback!
If you are interested you can upvote for a similar feature requests in this threads:
I hope this helps!