I suggest searching for help on Conditional drop down
https://help.quickbase.com/user-assistance/conditional_dropdowns.htmlMake a table of choices. You would need to populate the choices table by copying the choices from the multiple choice field and importing off the clip board into the choices table and then set the key field of the choices table to be the text choice value. Add a field for the category.
Typically, this is set up by having a table of categories (I suggest a Key field of the category). That way it would be easier to maintain going forward. So then you would make a relationship where 1 Category has many Choices and then assign the Choices to a category in grid edit.
Make a relationship where a Category has many Records.
Make a Relationship where 1 Choice has Many records - the actual record in your table. use your existing field for the reference field on the right side of the relationship.
Then set the drop down field to be conditional that after the Category is selected, then limit the choices to one where the category matches the one chosen on the record.
