Hey Mark,
Tulip Queries and Aggregations will unlock this for you.
You can add a query to a table named “All” which has no filters or anything on it. Then you can utilize a Unique Values aggregation on this query to get all the unique values in the ID column. Tulip apps will be able to utilize this aggregation just like an array variable. @John also put together a tutorial here where you can see a more complex version of this.
The only limitation worth noting is that the query and aggregation are limited to 1000 records. So there are situations where you will need to work around this. I do not imagine this is an immediate concern of yours.
Cheers.