A free mod for Witcher 3, by SorceressJ and pMarK.
XP Tweaks and Set XP Multiplier is a mod that adds several enhancements to the game. It allows you to customize the way you play the game, to increase or decrease your experience and abilities, or to simply tweak them for your own personal preferences.
This is a popular mod for the game, that allows you to choose the level of difficulty for the quests.
Installation:
You can download and install this mod directly. There are some settings that you need to change in your game, and this mod has a detailed installation guide that will help you change them.
About:
This mod includes several enhancements to the game, such as an option to increase or decrease your experience and abilities, an option to increase or decrease the level of difficulty for the quests, an option to increase or decrease the number of enemies for the quests, etc.