Can I import transaction data from closed exchanges like KoinEX?

You can do that through a custom integration process.

How to Import Trades to KoinX Using a Custom File

Open and make a copy of this Google Sheet: KoinX Custom Spreadsheet. (opens in a new tab)

Refer to this for sample data: KoinX Custom Spreadsheet - Sample. (opens in a new tab)

Fill in Your Trades

Enter each trade in the template using the required fields and formats.

Download the File

Save the sheet as an .xlsx file on your computer.

Upload to KoinX

Go to the KoinX Integrations Page and select the ‘Custom File’ Option.

Upload the file

To understand the process in detail - https://www.koinx.com/guides/integrations/how-to-upload-custom-file-koinx (opens in a new tab)