A while back, the company I work for used a free trial of the Table Grid Editor. It worked exactly how we wanted it to, but when we attempted to use it in the Service Desk Portal with Jira, the table didn't render. It just didn't show up. I've been looking through some of your latest documentation and see where you've released fixes for the Service Desk, but I didn't see anything on if it's compatible with the Portal portion of Service Desk.
We raised an issue back in 2013 to have support for a complex custom field in the context of JSD but up to now this support was not provided by atlassian.
We are planning to provide such compatibility using a completely reworked grid interface. Currently it is available on cloud (Table Grid Editor for Cloud) and a server version should become available in the course of 2018This feature is now available in Table Grid Next Generation for Jira Server.
You can download it from the Atlassian Marketplace.
We also plan to add this feature for Table Grid Next Generation for Jira Cloud in the future.