Hi Steve,
Specifically with Sync tables that are pulling the data in via Quick Base Sync you aren't able to import data in even if it is targeting the manual entry fields you have added to the table. This is because all add and delete record permissions are tied to the Sync. To add new fields to a sync table they either have to be added into the synced in source or manually entered on that table.
A work around I have used in the past when I want to import a sheet of data that is related to a sync table is to add a child table of related records that is manual entry. Then so long as my key field is in the data I'm importing in I can import in all the necessary fields and records as child records with the relationship being populated from the incoming data and since the child table is a normal QB field I'm not blocked from importing data in. Then I can either summarize data up to the parent sync table or bring down the sync table data through the relationship to build out my reporting. I hope that information is helpful.
------------------------------
Evan Martinez
Community Marketing Manager
Quick Base
------------------------------