The track ordering of the Editor and Mixer is synchronized: if you reorder in one window, the ordering in the other window will follow.

Reordering in the Editor Window

Select the tracks you want to move. Then use
Track > Move Selected Tracks Up (shortcut: ↑) or
Track > Move Selected Tracks Down (shortcut: ↓).

Alternatively, you can use the Tracks & Busses panel of the Editor Lists, if visible. Here, you can freely drag-and-drop tracks and busses into any order you prefer.

Reordering in the Mixer Window

Within the Strips pane at the top left of the Mixer window, you can freely drag-and-drop tracks and busses into any desired order.

"Collecting" Group Members

Tracks and Busses that are members of a group can be reordered so that they display contiguously within the Editor and Mixer windows. Context-click on the group tab and choose Collect.

Ordering of New Tracks

When adding new tracks, the current selection determines their placement. New tracks will be placed after the rightmost (in the mixer) or bottom-most (in the editor) selected track. If no tracks are selected, new tracks will be added at the end.

Because new tracks are automatically selected, you can quickly reorder them in the editor window via the keyboard shortcuts after adding them (see above).