Hi Caitlyn,
Thank you for sharing your question. I understand the missing arrow that opened the daily details in your Outlook Calendar’s monthly view. I get that it was a handy way to see your day’s plans fast, so it’s annoying that it’s gone. I am here to help.
This change is from Microsoft’s recent Outlook update to make things the same everywhere. The old To-Do Bar and daily details panel are gone in the New Outlook for Windows and online. Right now, you can't get the arrow or the old, pinned panel back. Microsoft suggests using the My Day panel instead. You can open it from the calendar icon with a checkmark in the upper-right corner.
My Day has two tabs, Calendar: Shows your daily schedule. To Do, shows tasks from Microsoft To Do.
If you like the old setup better, you can switch back to Classic Outlook (if your company lets you) or send feedback to Microsoft by going to Help > Feedback or the Microsoft Feedback Portal.
May I also ask are you use New or Classic Outlook? If you can still use Classic, I can tell you how to turn on the To-Do Bar to get something similar back. Just let me know, and I’ll give you the steps.
I hope this answer is helpful, if you have questions, feel free to reply.
Best Regards,
Noel