ChemDraw temporary label for chemnum LaTeX
The ChemNum package documentation that can be found on CTAN specifies:


  Create the scheme and place temporary tags like TMP1, TMP2 and so on where you want the compound labels to be.


A question on TeX.SX specifies:


  When you create a text box and type into it, it will store it as a string correctly in the EPS. However, it was (sometimes) automatically putting it into chemical formula mode - so that in TMP1, the 1 was subscript (TMP1). Even if you fix this manually, it now saves the TMP and 1 separately in the EPS, meaning CHemNum fails to find TMP1.


Thus, it seems all you need to do is create textboxes with the appropriate labels.