Hello Mabel Loi,
Thank you for reaching out to Microsoft Q&A and informed us about this issue. I believed that the change of the button where the chat panel moves to the top right corner is a design by choice by Microsoft to integrated and improve user experience. However, you can also submit your feedback via Microsoft Feedback Hub to let the developer knows and hopefully on the next update they can fix the issue and bring back the chat to the main page.
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.