[Merging pixel layers in Affinity Designer on a Mac]

I am following a tutorial where the instructor is using Affinity Designer on IPad. One step in her demo requires merging 5 pixel layers. On the IPad, the instructor selects the five layers, then opens the menu at the top of the layer studio, and clicks on  "merge selected" . On my Mac, the menu at the top of the layer sudio looks entirely different. (Sorry,I can't take a screen shot because my screenshot app does not take pics of pop-ups.) It includes optons like "Auto-scroll", "Checkerboard background", "Small, medium or large thumbnails". I am working in Pixel persona. I looked in the main layer menu, but that does not have a "merge selected layers" either. Where is that option on the Mac version of Affinity Designer 1.9?