Show separate tree
The option Separate tree allows to show either one, two or no separate tree panel. Separate tree panels are show in addition to the two file panels, and can show only an expandable (but not a fully expanded) directory tree. You can expand/collapse branches of the tree using the + and - buttons on the numeric keypad, or by clicking on the +/- sign to the left of the folder icon, just like with the tree view inside a normal file panel.
If you choose to show one separate tree, it will show and scroll to the current directory of the active panel. If, however, you choose to show two separate trees, each panel will have its own tree.
The tree isn't expanded initially to make Total Commander load faster. It will be expanded the first time you change directories, or swap panels.