There are JDBC drivers available for all commonly-used databases and Excel and CSV files. Therefore, you can connect to a spreadsheet containing a list of items you want to be available in a custom field.
First, add the spreadsheet as a connection in setting up an external database connection.
Create a scripted field.
Give the field an appropriate name and description then enter the following intoRetrieval/Validation SQL:
select id, "First Name" || ' - ' || "Experience Level" from devs where id = ?CODE
Enter the following intoSearch SQL:
select id, "First Name" from devs where "First Name" like ? || '%'CODE
When applied to an issue context, the results display as a drop-down: