referring to parent directory in a save file dialog

Backslash has another meaning in Linux: it escapes the special meaning of a special character so that the literal character is used. For example . can mean the current directory or in some contexts 'any single character'. \. means a literal dot. Before a normal character, for example an ASCII letter, backslash makes no difference unless that character is also used to represent something else (e.g. \t is a tab and \n is a newline). When the character has no other meaning, for instance a, then escaping it has no effect: \a is a.

So

touch ..\asdf

will create the hidden file ..asdf. (It is enough with one dot in the beginning of the file name to hide it.)

Linux uses forward slash to separate between directory and file names in the path.

touch ../asdf

will create the file asdf in the parent directory.