Be able to select several value in a cascading select list

Hi all,

We are using a cascading select customfield which allow user to enter the module and submodule relating to the issue.
When developers are searching for issues, they would like to be able to select more than one value on the submodules (several value in a cascading select list).

"Currently the submodule selection field is single-valued, it would be good if one could query on several submodules at once."

What could be the best solution to meet this need ?

Thanks in advance.
Cheers.
Pierrick.