Yad - Yad (yet another dialog) is a fork of Zenity with many improvements, such as custom buttons...
wxWidgets - wxWidgets: Cross-Platform GUI Library
Glade - Glade is a RAD tool to enable quick & easy development of user interfaces for the GTK+ toolkit...
Electron - Build cross platform desktop apps with web technologies
wxFormBuilder - wxWidgets is an excellent framework that enables the creation of multi-platform applications with...
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.