import and split all paragraphs

is it possible to import and split all paragraphs?

Yes, if you use the File > Import > Import and Split command and specify a carriage return as the separator, then you’ll end up with every paragraph in its own document on import. You may need to do a little cleanup afterward if you also have single line titles or such for different sections, since they’ll end up as their own document too, but that should be fairly easy to do, or to use those as containers for grouping the other items beneath, etc. depending on how you want to structure your work once you’ve imported it.

which is the carriage returns symbol to write in character separator?

Just press the Enter or Return key; you don’t need any special modifiers.

in this case the paragraphs is not splitted

Hm, are you up to date with version 1.5.7? You can check your version number in Help > About Scrivener and update via Help > Check for Updates if need be. You should be able in 1.5.7 to use a carriage return for the splitter (delete the default # splitter or whatever is already there, then just press Enter) and import the document with each paragraph–which I’m assuming is delineated by a carriage return–in its own document, and any extra white space between paragraphs removed. Does the document you’re trying to import have a lot of fancy formatting? I’m not aware of any issues with splitting this way, but I suppose something like that might be throwing things off.

when I delete # splitter appear popup that say: file separator cannot be empty

I have last version 1.5.7.

Just to be clear, after you delete the # are you pressing Enter while the focus is in that text box, so that a carriage return symbol appears in the box? I realise I may have made it sound that pressing Enter is for submitting the settings in the dialog, equivalent to pressing the “OK” button, but you need to be typing the key while the focus is in that Separator field so that it is seen as the separator:
If that’s still not working, are you working on Linux or Windows? I notice your profile says Linux, and it’s possible there’s a platform discrepancy here I need to check on.

bingo! carriage return focus in the separator field work but not copy and paste character carriage return,
many thanks.