On the KWin side it is enabled by setting an environment variable
KWIN_WAYLAND_SUPPORT_XX_SESSION_MANAGER = 1
Should be in since Plasma 6.4.
For application side I found this information for Chromium
Both Chromium and Chrome on my system have the chrome://flags/#wayland-session-management option, Edge does not.
Haven’t checked if any of my Electron based apps understand the associated command line switch.
It seems I remembered incorrectly about Firefox having support as well.
Their ticket for this is still open without any patch.
For Qt the environment variable to set is
QT_WAYLAND_ENABLE_XX_SESSION_MANAGER = 1
and apparently landed in Qt 6.10.
Haven’t checked GTK, however since Mutter has support for this as well there is a high chance this is also supported in their primary toolkit.