This is a Serious Sam Rev Name Editor alternative, made by Angelo, the Croteam developer.
Just point the program to your .plr files and edit them.
Question: Where can I find the controls, players (for name tag making/editing), scripts folders.
Here's the answer:
Controls/Players/SaveGame/Screenshots/PresistentSymbols.ini: [your Steam folder]\userdata\[your steam account id]\227780\local
Scripts: [your Steam folder]\steamapps\common\Serious Sam Revolution\Scripts
Use these files at your own risk!