From Einhugur Software:
REALbasic WindowSplitter plugin control to create split view in forms. Has REALbasic style splitters, native MacOS X and Linux splitters, Outlook style splitters and ability to custom render splitters. Can compile for MacOS Classic, MacOS X, Windows x86 and Linux x86.
What's new in this version:
8.6 adds HiDPI and Retina toolbar icons for design mode with Xojo 2016 and later.