I want to open 2 project files in separate windows to view them side by side... but each time I try, it opens them in the same window

Dear Tslme

Good day! Thank you for posting in Microsoft Community. We are happy to help you.

Based on your description, we do understand you want to open 2 project files in separate windows to view them side by side.

Per our test and search, we have to tell you that there not a direct way can do this in Project. But you maybe can do the following as an alternative.

Some users mentioned that you can view one project in the upper pane and the other in the lower pane by opening both projects and then selecting View/Window group/Arrange All. Please kindly have a try to see the outcome.

Here is the similar thread, you can have a reference: Two MS-Project windows side-by-side - Microsoft Community

And this one: Opening and Viewing Option for Two MS Project Files Simultaneously on Two Screens? - Page 2 - Microsoft Community Hub

Besides, we kindly suggest you submit feedback in Project · Community (microsoft.com) . It is the best platform for the developer team to listen to your opinions and make the products better serve you and others. The Product Team is in-charge of the feedback site, and they are constantly checking the comments and feedback from our customer. Many features have been developed or improved based on users' comment.

Your understanding and patience will be highly appreciated. I hope that you are keeping safe and well!

Sincerely,

Stacey | Microsoft Community Moderator