To delete a knowledge base, go to Company > Knowledge base section > select the knowledge base you want to delete > click Actions > Delete knowledge base.
After you've deleted the knowledge base, it's automatically moved to the recycle bin and is stored there for 30 days. To view knowledge bases in the recycle bin, click the Recycle bin button or use the corresponding filter.
Knowledge bases in the recycle bin have a special counter showing days left until irreversible deletion.
You can restore the deleted knowledge base during these 30 days by clicking Actions > Recover knowledge base.
Only a user having the appropriate access permissions can delete a knowledge base. Read more in the article - Company knowledge bases access permissions.