Swim2 - CSV downloading and uploading the same file doesn't work

Zip then insert the file into your post. We might be able to tell you what is wrong.

activity_8297870119.zip

Here. This is the exact same file I've downloaded from Garmin Connect website, using the function "Export Splits to CSV"

4081763 said:

I'm trying to upload a CSV file downloaded from Connect website.

Sorry, guess I didn't understand your problem If you're downloading splits, you can't upload those same splits and expect that to work. The upload is intended for importing a complete activity, not just splits.

So I can't edit the splits and the upload them back again, correct? If so, that's very disappointing. I don't understand the utility of downloading and uploading a complete CSV file for the whole activity if I can't edit the single splits, but maybe I'm understanding it wrong 

If you need to edit splits, that could be done using a 3rd-party tool, such as Fit File Repair Tool. Or if this is a swim, the online tool Swimming Watch Data Editor.

Fit File Repair Tool is not free, Swimming Watch Data Editor do some trick but missess lot of fundamental functions (i.e. add some lap that has not been recorded9. I'm a bit disappointed about this: I thought that download and edit  a Garmin activity would be one of the easier things to do, whereas I find that it's impossible (for some unexplicable reason) even to download and edit a CSV file.
I work as an I.T. programmer for a small company that makes web applications, and we have no software without an import/export CSV functionality because it's quite basilar to have it in 2022.

I expected more from Garmin