As name suggests, this is the Relative Layout Extension for MIT App Inventor2. It allows us a placement of MIT App inventor 2 visual component.
Beside its complete code, one can here also find its aix file so that one can immediately use it, as well as an aia file for simple RLE Demo that showcases its use.
Please note, newest version of aix file is tomislavt.extensions.RelativeLayoutExtension.aix. Older version is still here becouse it is of use to some.