Dividends Inside can import trades from three supported sources: a manual default file, an Interactive Brokers activity statement, or a DeGiro transactions export. Lot Management and portfolio settings exports use the same columns as the default import, so you can export, edit, and import those lots again later.
Create a file yourself when your broker is not supported directly or when you want full control over the imported trades. You can also start from a Lot Management export or the portfolio settings Export positions file, make edits in your spreadsheet app, and upload it again. Save the file as .csv, .xls, or .xlsx.
ticker,date,action,avg_price,amount.ticker,YYYY-MM-DD,buy|sell,price,shares..xlsx. ticker,date,action,avg_price,amount
MSFT,2022-01-10,buy,310,75
AAPL,2023-05-12,buy,172.35,12
KO,2024-02-01,sell,59.10,5ticker: The ticker symbol you want to import.date: Trade date in YYYY-MM-DD format.action: buy or sell.avg_price: Average price paid per share.amount: Number of shares in the trade.ticker,date,action,avg_price,amount. This makes them suitable for backup, spreadsheet edits, and later re-import with Default CSV / Excel selected. 
In IBKR, go to Performance & Reports and open Statements.

Generate an Activity Statement, set the correct date range, and download the result as CSV.

Use the Transactions export and keep the broker-generated layout unchanged before uploading it.
If your file still does not preview correctly, double-check that the selected import format matches the file you uploaded. You can also use the report form if your broker export looks correct but is still rejected.