Shortcut to change layer/add via whilst routing in Eagle
This is certainly possible in Eagle using commands.

When using the route tool, the following command will instruct eagle to change layers:

layer &lt;layerNum&gt;


Where &lt;layerNum&gt; is the layer you want to be on. If you are currently in the process of routing a trace, Eagle will switch to the new layer at the last point that you clicked and add a via at that location.

If you are using the wire tool, eagle will change layer but it will not add a via when it changes the layer.



It is also possible to assign shortcut keys to perform this action. If you select Options-&gt;Assign... from the menu in the board editor you can then create a new shortcut. 

Select a key + modifier (e.g. Ctrl+1), then as the assigned command, enter the layer command (e.g. layer 1). Ok that to create a shortcut. 

Now when routing the trace with the route tool, simply press the keyboard shortcut you created and the trace will jump to that layer.