Actually it seems I can import one column having more than 255 chars like this.

global
procedure ImportTestIn(record RcVc RepSpec)
begin
string 255 tstr;
record NotepadVc Noter;

tstr=ImportField;
tstr=ImportField;
if(ImportIntoText(Noter)) then begin end;
tstr=ImportField;
while (NextImportLine(false)) begin

end;
StopAlert("tstr=" & tstr);
OpenWindow("NotepadDClass",1,0,"","",Noter);
end;