Folder Tree Does Not Stay

I am new to Directory Opus. Can someone tell me how to make Folder Tree stay in the left most part of the Lister? After placing the File Tree by pressing F8, I closed the Lister. When I re-open the Lister, the Folder Tree is nowhere to be found. There must be a quick and easy solution for this. Your help would be appreciated. Thank you so much!

After turning on the tree, use Settings > Set as Default Lister.

It worked! Thank you! Ken