Student version Labview 7 Express Fig. 9.4 illustrates sting and number concatenation. I see that there's a control to "trim whitespace". The "format into string" control should facilitate the insertion of a space between concatenated strings by allowing you to mandate the insertion of a single space where none already exists. Even the example provided (Fig. 9.4) requires the appending of a single space at the end of the initial string.
Could you explain what you mean? The Format Into String function does allow for inserting spaces or any other character between, before, or after. For example, if the format string is "%s %s" and you have input strings "a" and "b", the output will be "a b".