Hello,
somewhy I am not able to edit effects anymore. When I am putting effect on clip, I see a hit - enable edit mode in monitor.
how to do it?

it is much easier to find it in source code, but not in UI


if ((m_sceneVisibilityAction != nullptr) && !m_sceneVisibilityAction->isChecked() && sceneWithEdit) {
// User doesn't want effect scenes
pCore->displayMessage(i18n("Enable edit mode in monitor to edit effect"), InformationMessage, 500);
type = MonitorSceneDefault;
}

Project or clip monitor: Click the 2nd icon right to the play icon. These show/hide the edit mode. The icon with the doted square that has on each corner a dot.