IntelliSense doesn't give information about the formatting options for the .ToString() method on the Guid type:
The format parameter can be "N", "D", "B", "P", or "X". If format is null or an empty string (""), "D" is used. https://docs.microsoft.com/en-us/dotnet/api/system.guid.tostring?view=netcore-3.0
Hello
That text is for the format parameter, you'll need to navigate to the appropriate overload. It displays for me when I navigate to it:

I can see what you see now. However, it doesn鈥檛 say what those options do.
Intellisense only displays the simple summary information, not the detailed remarks. You would have to push F1 while the caret is on ToString to see more detailed information. Otherwise, the intellisense would be too big and cover too much of your screen.

Today I learned that F1 takes me to docs.microsoft.com.
I forgot about it too until I was working on this issue. heh
Most helpful comment
Intellisense only displays the simple summary information, not the detailed remarks. You would have to push F1 while the caret is on ToString to see more detailed information. Otherwise, the intellisense would be too big and cover too much of your screen.