Arduino IDE stores data under five separate external folders. So if you want to make a fresh installation you should delete all of them:
Sketchbook Folder
The sketchbook folder location is configured via the Arduino IDE preferences.
You can determine the location by selecting File > Preferences from the Arduino IDE menus and then checking the path shown in the "Sketchbook location" preference.
Configuration Folder
This folder is located at the following path:
C:\Users\<username>\.arduinoIDE\
(where <username> is your Windows username)
Data Folder
This folder is located at the following path:
C:\Users\<username>\AppData\Local\Arduino15\
(Where <username> is your Windows username)
User Data Folder
This folder is located at the following path:
C:\Users\<username>\AppData\Roaming\arduino-ide\
(where <username> is your Windows username)
Temporary Folder
This folder is located at the following path:
C:\Users\<username>\AppData\Local\Temp\arduino
(Where <username> is your Windows username)
If looking for it with your file manager or command line, note that the AppData folder is hidden by default. On Windows "File Explorer", you can make it visible by opening the "View" menu, then checking the box next to "☐ Hidden items".