Should this option be working for import?
Because in my tests, each imports, system duplicates all lines in CSV, even the key selection is the same (for example, I redo the same csv file).
This part of the application is really used a lot and tested. I just did a quick test skipping records I had just exported and it worked correctly.
You believe problem can be, about a special characters use in Portuguese language ?
For me:
1) I saved custom map, and when I returned, many fields is wrong, different I saved;
2) System not skip or merge when I tested filed name and lastname;
3) If list have a item accentuated or capitalized, the system duplicates the entry in the lists.
Doubt I can use each another field for testing for merge registry?
For example, I can user firstname, lastname combined with a CF field?
Yes, I think that should work correctly, you can select them in step 3 and I suppose that it is just another field.