To add or update metadata on your Figma comments, make sure the Figma Comments tab is selected, then click on any Figma comment card to open up its details panel in the plugin.

Once you've clicked on a Figma comment, under the Overview tab in the comment details popup panel, you can populate any metadata you like, which will be saved in real-time, and will be visible from the main kanban board, and from the same Details panel.