Subobjects Converter is a MAXScript for 3ds Max, created by Nik, that converts between subobjects using keyboard shortcuts. The developer positions it as a tool for working in Expert mode.
Beyond plain conversion, it adds a set of extended actions triggered with Esc-key combinations. Esc+1 toggles Soft Selection on or off. At the edge level, Esc+2 makes hard edges when edges are selected and smooth edges otherwise, while a further shortcut caps a hole when edges are selected. At the face level, Esc+4 makes hard or smooth edges around polygons depending on the shortcut. At subobject 5, the script switches to the Element subobject for Unwrap UVW when that editor is open, or enables the usual level. With all faces selected at Face or Element level, pressing a script key opens the Smoothing Groups floater in a separate window.
The script installs by dropping the .ms file into the viewport. This card covers version 3.07, and the plugin is listed here as free.