Reducing the size of the Save As dialog box in Excel can be done by following these steps:
In the same tab, uncheck the Display hidden files, folders, and drives. This will help you focus on the task at hand and not get distracted by other files on your computer.
4. Under the View, go to the bottom and check the option that says Always show full menus. This will help you see all of your options when you right click on a file or folder.
5. Under the same tab, go to "Other settings" and check "Launch folder windows in a separate process".
This will help improve your computer's performance when working with large files or folders.
6. The last thing we can do to improve performance is to change how often Excel saves AutoRecover information. By default, this is set to 10 minutes. You can change this by going to "Save" under File         Options.(1)(2)(3)(4)