This page of our guide to Wolcen Lords of Mayhem has information on how to reset a skill tree. This option can be useful if you want to change the class of your hero during a playthrough.
The option to reset passive skills (skill tree) is located in the attributes. Just go to this section and you will have two options.
You can reset attributes - after paying a certain amount of gold. If you want to reset the skill tree, you need Primordial Essence.
If you want to know how to get Primordial Essence, check out the separate page of the guide, where we have described in detail what Primordial Essence is used for and where to get it.
After resetting the skill tree, you will receive all previously spent points. It is up to for you to decide how you want to spend them.