I thought this could be done when setting up the verb by dividing the words with semicolons, but apparently not. So a workaround is to set all the verbs up individually and then copy the code across but the game isn't letting me do that either for some bizarre reason. I'm trying to use the verb push and add aliases shove and move. I add the code to the new verb and then test the game and it doesn't work. When I go back to look at the script the game has simply disregarded (deleted) it. Is there a simple way of doing this?

Ignore this, it works now. For some reason the game wasn't saving my changes. I found that pasting the code then clicking on another object worked.
The initial question of adding aliases still stands though if anyone knows an easier way?

It should work with semi-colons to separate them. Here is an example of one that works for me:

<verb>
    <property>rotate</property>
    <pattern>rotate; turn; twist</pattern>
    <defaultexpression>"You can't rotate " + object.article + "."</defaultexpression>
  </verb>

ETA: Be aware there are two parts to a verb. The verb object itself, like that above, and the script on another object. The script on the other object is on the "rotate" attribute in this example, but that is really just a name for Quest; the player never sees it.

The aliases go into the verb object, and as Quest quietly creates these for you it is easy to miss they even exist. Look for them under the game object. Many are built-in too.