That's still event handling. You can do basic binding between outputs and values, but more macroscopic changes (closing a dialog, changing tabs, etc) requires tracking the state your UI is in, and manually transitioning.

This is markedly different than React, where the framework diffs the desired UI state (which is a pure function of your application state), and the actual UI state. The minimal number of UI operations necessary is then applied to make the latter match the former.

ImGui above works the same way, which makes it very popular for devtools in game development.

ImGui is quite similar to MS-DOS game UIs, before we migrated to Windows.

The source code of quite a few ones is available around the Net.