I added a new forum section called, Atheism & Secularism. I figured that agnostics and others would not simply want to debate on religious topics but also topics that deal with atheism.
 
Update: 8/14/2021 Regarding an overlap in topics and forum categories (i.e. the Non-existence of God forum category and God's existence forum category):

The two forum categories would obviously cause some overlap since both deal with the issue of God's existence. However, I still want a forum section for Atheism and one for Theism. So instead of eliminating an important part of atheism, such as the non-existence of God, I've decided that you can make topics for the non-existence of God in two sections of the forum. But if you want to have special or more focus on your argument against God, then I'd recommend posting it in the Non-existence forum category since that section is dedicated only to God's non-existence.