HEXOstudios is free on the Mac App Store, with no limit on how many files your library holds. Free includes importing files and folders, Smart Search, Batch Rename, and unlimited thumbnails and 3D preview for STL, OBJ, PLY, AMF, USDZ, Rhino, FreeCAD, GLB/glTF and FBX, toolpath cards for G-code, plus 12 unique 3MF files and 12 unique STEP files, for life.
Pro adds nested folder import, Full 3D Preview, File Passport with notes and tags, Send to Slicer, Project Queue, Library Health, Visual Export, HEXOforge and Workspace Glow, and previews unlimited 3MF and STEP files.