TM: how to create value for "empty value"?

There are lots strings in my TM sources on Crowdin with an “empty value” instead of translation.

First, where did they came from, as I did not uploaded this amount of strings?

And second, how can I edit them in-program, is it possible at all? When I click “edit”, I can only edit an english part, there simply is no field for translation.

Probably some untranslated, like duplicates or some hidden stings. Maybe some metadata strings like image-alt and so on. Use filter in the project to see only not translated + hidden, or copy the English field into the editor search to see where it come from. Probably article will help you

But I’d say you can leave those TM strings untouched as they affects nothing. Once you translate a content, anyway it will go into the TM as well.