Hi @mirkomen77,
Welcome on OpenDataKit forum. Please don't hesitate to introduce yourself here : Introduce yourself here! - #994 by Jackson_Jackson
For the problem you are facing, you will have to manage your list in a media (csv) file and make use of the pulldata and probably search() functions.
I don't know hows to do it with the builder bur here you'll find a complete example we create in course with the french national taxonomic reference (in fact a subset of the national taxonomic reference but we use quite the same every day with a 200000 lines taxonomic list)