[zorr]

From what I've seen the .ui format for Gtk3 and Gtk4 are different and Glade does not support Gtk4 Widgets or its additional libraries like libadwaita.

Cambalache is a successor for Glade but it also has issues. It uses its own storage format and you have to export to a .ui file for use in your Gtk4 project, and if you make changes to the UI file it's very difficult or even impossible to use those changes in Cambalache again.

The general consensus on a few of the GNOME-related Matrix channels seems to be writing .ui files by hand.