Similar to the Oxenfurt Drunk Fix by NoPreference this mod solves the annoying red cross/failed objective in the In the Heart of the Woods quest. After you've installed the mod follow these steps:

• Examine the tracks in the wood
• Talk to Harald, select "I'll try it your way"
• Approach the altar, kill the wolves and collect the wolf hearts
• Talk to Sven and finish his quest line by killing the leshen
• Collect your reward and enjoy your green marks
  

Few notes: With this mod you'll have to eventually kill the leshen, Haralds path will not finish the quest. Also the green marks remain when you delete the mod afterwards. However you have to install the mod before you start the quest, it will not work retroactively.

How to install:

• Download and unzip modQuestFix.zip
• Move the folder modQuestFix to <game_path>\mods
  

How to uninstall:

• Remove the folder modQuestFix from <game_path>\mods
  

My other mods:

• Hair for Yennefer
• 4K Armor Textures
• Enhanced Graphics Settings
• Faster Sprint Stop Animation
• Slim Gloves
• Heart of the Woods Quest Fix
• Alternative Witcher Scabbards
• Unified Oil Icons