I usually use a globally accessible .csv file with a single entry value in it (because it is faster getting to finalized), but this always works in a pinch. Just toss this after your description and before everything else.
<query>index=* | head 1</query>
If that's a token the user can modify, set the default value for the input the user uses to modify the token.
If that's a token the user can't modify, replace the uses of the token with the value you'd like the token to have.
If those two approaches don't do what you need, please describe what you need rather than what non-working solution you have in mind.
If that's a constant, consider declaring a macro and use that. Bonus: Declare once, use in all dashboards.
setToken() function at any time you please.