No. Currently JMIR supports the display of only one corresponding author.
However, we can generate a footnote saying that all or a certain number of authors (e.g. first and last author) contributed equally to the work. To generate the footnote, click the checkbox "equal contribution" in the metadata form for each author which should carry this footnote.
In addition, authors can use an "Authors Contribution" section within the manuscript (after the "acknowledgements"), see What is the "Authors' Contributions" section? How should I write mine?