There is no "multi" property for a text box, so i assume you mean including line endings to make it be on separate lines. Since there's no -a to append new text to the end of an existing text box, the limit would be how long can be the line length of the /did command, which should be in the neighborhood of $maxlenl plus small. For appending extra lines, you can squeeze a little extra text by ending the lines with $cr instead of $crlf.
