It's good to have you again in the QuickBooks Community forum, Tania.
Before anything else, could you please clarify whether you're using the web-based QuickBooks Online (QBO) platform or the QBO Desktop App?
For the web-based QBO, you'll have to first open multiple tabs by right-clicking your browser tab and selecting Duplicate or Duplicate tab. Afterward, you can drag the new browser tab into a separate window. In the new tab or window, you can navigate to other sections to view different areas side by side. Any updates you make will sync across all open tabs or windows automatically.

You can also right-click on specific menus within QBO to open them in a new window.

Now, if you’re using the QBO Desktop App, click the + (plus) icon in the top-left of the app and select or search a company to work with different sections simultaneously.

Alternatively, if you meant something different, please do share further details about it in the comments below.
As always, the Community and I will be here to ensure you have all the help you need.