|Atlassian Update - 1 April 2021|
Thank you for your feedback on this ticket. Based on your feedback, we have identified this ticket as high priority. Although we cannot commit to dates at this time, the display of Trello cards on the new issue view (through the Jira Power-Up extension) is on our short term roadmap. Please watch this ticket for updates.
The Atlassian Cloud team
You can install a Jira Power-Up (extension) in Trello and you can refer to Jira issues in Trello cards.
When you do it, in the old issue view it's added a section called "Mentioned in" which shows the link to the Trello card, but this is missing in the new issue view.
As a Jira user, I was to be able to see the 'mentioned in' section related to Trello in the new Jira issue view.