Ardour does not impose any particular ordering of tracks and busses in either the editor or mixer windows. The default arrangements are as follows:
In the Editor window, the Master bus will always be on top unless hidden. Tracks and busses will appear in their initial order, from top to bottom. The monitor section (if used) is never visible in the editor window.
In the Mixer window, the tracks and busses will be displayed in their initial order, from left to right. The Master bus is always on the far right and occupies its own pane, so that it is always visible no matter how many other mixer strips are present. If a Monitor section is used, it shows up at the right edge of the mixer window; it can also be torn off into a separate window.
The track ordering of the Editor and Mixer is synchronized: if you reorder in one window, the ordering in the other window will follow.
Select the tracks to be moved, then use Track > Move Selected Tracks Up (shortcut: ↑) or Track > Move Selected Tracks Down (shortcut: ↓).
Alternatively, the Tracks & Busses panel of the Editor Lists can be used, if visible. Here, tracks and busses can be freely dragged-and-dropped into any desired order.
Within the Strips List pane at the top left of the Mixer window, tracks and busses can be freely dragged-and-dropped into any desired order.
Tracks and Busses that are members of a group can be reordered so that they display contiguously within the Editor and Mixer windows. Right-click on the group tab and choose Collect.
When adding new tracks, the Insert: field allows to determine their placement. New tracks will be placed Last by default, so 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, regardless of the choice.
Because new tracks are automatically selected, they can be quickly reordered in the editor window via the keyboard shortcuts after adding them.
Every track and bus in Ardour is assigned a remote control ID. When a control surface or any other remote control is used to control Ardour, these IDs are used to identify which track(s) or buss(es) are the intended target of incoming commands.
Remote IDs are assigned to tracks and busses in the order that they appear in the mixer window from left to right, starting from #1; manual assignment of remote IDs is not possible. The master bus and monitor section can be accessed by name.