We’ve created a version of this in the Form Engine to replicate Quickbase native functionality, because the QB API doesn’t support pulling the native functionality through. So set up the conditional dropdown functionality in native QB as QB prescribes, but with these differences in the configuration of the Reference field that is the conditional/filtered list field:
Then you’ll be using 2 Related Parent fields in your form, where one is set up in QB above to be conditional on the choice a user chooses in the other. Open the Field Properties in the 2nd field, that is conditional on the first, will bring up this section. Clicking the blue button will load the current QB data from those fields.
The dropdown options will not update with changes in the source QB data, they are static in the form, so to update them for new values, you have to go back in when there are new values and click Update. If it becomes technically possible to improve this over time, we will improve it.
You can expand the conditional dropdown to 2 or more cascading dropdowns, too, by repeating the process above with a new table(s), relationships, reference field configuration, and using the blue button above for the new “related parent” fields on your form.