A professional diagramming tool that helps users visualize complex information through easy-to-understand diagrams.
Based on the user's requirements shown in the image (mapping a machine in three simple parts: Machine itself, Attachment Parts, and SPS Control Unit, and pointing out spare parts without needing complex processing), here are the best simple tools outside the Microsoft ecosystem that fit the bill:
Bullet Draw.io (Diagrams.net): A free, web-based diagramming tool that requires no installation. It is ideal for importing machine photos and adding callouts, text boxes, and directional arrows to point out spare parts across different sections.
Bullet Miro or FigJam: Collaborative digital whiteboards that allow you to easily drop in images of your machinery, group them into structural blocks, and use simple shapes and lines to highlight components and spare parts.
Bullet Excalidraw: A lightweight, minimal virtual whiteboard with a hand-drawn aesthetic that is very quick and easy to use for simple layout sketches without a steep learning curve.