I really see a big mess here; however the solution is very simple. Even no restart needed.
To my case I saved the flutter folder in my account's source folder and I appended this value in the PATH entry;
%USERPROFILE%\source\flutter\bin
Note: I only had one value and it was for Microsoft WindowsApps (;
Explanation
Now, we all know that we need to append "the full path to flutter\bin" in the PATH entry or create a new one if it doesn't exist. However, Windows users have different profile folders thus our case for the full path. So to solve this common problem whatever was the typical path for the user's profile folder, we can use %USERPROFILE% value which is a Constant special item ID list (CSIDL). See Recognized Environment Variables
Constant special item ID list (CSIDL) values provide a way to identify folders that applications use frequently but may not have the same name or location on any given computer.
So if you saved the Flutter folder, like me, in the user's profile folder, Just copy %USERPROFILE% and paste it before the flutter's bin folder directory in the PATH entry and then append all to the existing values using ; as a separator or similarly click the New button on the right side of the panel and paste it.