Integrated nanophotonics faces challenges in matching the component density of electronics, largely due to the size limitations of silicon-based photonics. High-refractiveindex materials like InGaS3 offer a promising solution for miniaturized visible/UV photonic circuits. This study demonstrates the fabrication of InGaS3 waveguides using mechanical scanning probe lithography (m-SPL), overcoming limitations of conventional lithography techniques. Test cutting in various directions shows that m-SPL trench quality in InGaS3 depends on crystallographic orientation, with zigzag-aligned force producing clean edges while jagged armchair-direction leads to fractures. The method allows to simultaneously determine crystallographic axes and optimize waveguides side walls quality. This approach establishes m-SPL as a viable route for nanostructuring unconventional materials where standard etching protocols fail, advancing high density integrated photonics.