When the parties of a German governing coalition disagree on fundamental questions, they take the dispute to the Koalitionsausschuss, the coalition committee. It is an informal body. The Basic Law does not provide for it. German Wikipedia cites a study arguing that it suits conflict better than the cabinet, because the small group know each other and are verschwiegen, discreet.
In March 2023 the leaders of the SPD, the Greens and the FDP met in the Chancellery from Sunday to Tuesday, for about 30 hours net. Winfried Kretschmann, the Green premier of Baden-Württemberg, said that holding 19-hour sessions was indeed ein Zeichen von Führungsschwäche des Kanzlers, a sign of weak leadership by the chancellor.