You need to create your own error logs. Create a new entity Errorlogs and a new entity ErrorlogDetails. In the Errorlogs make a attribute that holds the total number of errors. With every import make a new Errorlog. Now when you trigger the microflow that does the import and validations make sure that every time you want to log an error, create a new ErrorlogDetails with the specifics of the error (and make sure that the reference is set to the ErrorLog) and add one to the total number of errors.
This way you have all the errors after the import to your disposal.