In Altium Designer, how can you set the autotracer to route all traces with as equal lengths as possible?
You'll probably need to define a Matched Net Length Rule (Design -> Rules) where as "First Object" you will need to define all your Tracks. A query like "IsTrack" might be enough. Alternatively you can place all the tracks which need to be length matched into a net class and then define InNetClass('YourNetClass') as query. Set the tolerance to a value of your choice.

If the Autorouter doesn't obey these settings (I'm not quite sure about it) you can use the interactive length matching command (Tools -> Equalize Net Lengths) or the Interactive Length Tuning Tool (Tools -> Interactive Length Tuning Tool).