Thank you for contacting Skyvia Support team.
Skyvia does not support NetSuite fields, storing array data. Skyvia cannot extract data from such fields, and they are not displayed in Skyvia interface. If such a field is required in the table (must be filled in order to create a new record), Skyvia cannot load data to such tables. So, such tables are read-only in Skyvia. Opportunity object is read-only that is why it can't be used as a Target in the Import Package.
The full list of such objects includes all the transactions objects because Skyvia cannot extract their items.
You can find more information about such objects as well as the full list of them in the NetSuite-Specific Features and Limitations section:
Please let us know if you need any further assistance.
Customer Support Engineer