You might want to open two files in two separate windows to compare them. Also, if you want to edit two files simultaneously, you need to open them separately. That is why you can change Notepad ...

When trying to open a large file, around 500 MB to 2 GB, applications like Notepad and Notepad++ fail as they do not support these file sizes. Notepad was meant to take a quick look into smaller log ...

Thankfully, you can still re-enable the old version of Notepad by opening the Settings App (press Windows+i) and navigating to Apps > Advanced App Settings > App Execution Aliases ...