Apologies that it’s not obvious about the relationship between nat, arco and bowed. ‘Arco’ is the name of the Playing Technique object in the score, which triggers a Bowed Playback Playing Technique (aside: we may rename these just ‘Playback Techniques’ to make this very slightly clearer). The Bowed technique is an alias for the ‘Natural’ technique. In Expression Maps the first step is to create the entry for ‘Natural’, and then add pizz, legato, etc.
We’ve tried to cover as many bases as possible with the set of underlying Playback Playing Techniques, but the set won’t be complete. Not all of them have corresponding score objects in the Playing Technique panel, however this still allows you to define your own desired P.T. appearance but trigger a known Playback Playing Technique (and if you can’t find one that’s suitable you can create your own too). I can see that we define Double Tongue, Triple Tongue, Flutter-tongue, Slap Tongue, Tongue and Finger Click, Tongue Click, Tongue Stop. But not ‘tongued’ or ‘multi-tongue’. I’d suggest that you select one that seems the closest - in most cases it doesn’t really matter unless you are sharing expression maps and playback templates with other users.