This is listed as a known bug in the module. The work around to fix the ordering in the documentation, which I have included here.
https://marketplace.mendix.com/link/component/108605
Create a (non-persistent) entity that reflects your CSV structure (columns). The names of the attributes should be ordered alphabetical in respect to the CSV.
E.g. a CSV having the following contents: ID,Username,FirstName,LastName
1,jdoe,John,Doe
Could have an entity with the following attributes to maintain an alphabetical order:
I hope this helps.