Hi @Rohan,
Welcome to the Microsoft Q&A forum.
Thank you for contacting us. I would like to provide you with the following information:
If you would like to change the To Do tag from a circular shape to the old square shape, please follow the steps below:
- Step 1: Click on the tag

- Step 2: Select Customize tags
- Step 3: Select Modify tag

- Step 4: Click on Symbol and choose the old square shape

I hope this information is helpful. Please follow the steps above and let me know if it works for you. If not, we can work together to further investigate and resolve the issue.
Thank you for your patience and understanding. If you have any questions or need further assistance, please feel free to leave a comment on this post so I can continue to support you.
I look forward to continuing the conversation.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.