Tree-structure for boards

Hi,
we have been using Miro a few years and love it, we have around 600 boards now. However, we are finding it more and more problematic to arrange boards so we can find our work. Is there any way to create "main projects" like "Marketing" with Sub-projects like "Presentations", "Displays" etc.
We have sooo many boards, and with only the name and creation date to base search on, we have trouble finding the latest version of work.
We need a tree-structure for Main Projects with Sub projects.