To use this feature, click on the Page icon button in the top left header of the plugin, then click the Re-Order & Tidy Figma Slide Layers button to instantly tidy up the slides on your Figma page into an ordered grid.
You can also tweak the number of Slides Per Row by using the select dropdown input, and also toggle the Add Fade to Unchecked Slides option, which will ensure that the layer opacity is set to 30% for any slides in the Pitchdeck plugin that have been unchecked (to exclude them from any exports).