from qgis.PyQt.QtWidgets import QWidget, QVBoxLayout, QLabel, QLineEdit

class TabA(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        layout = QVBoxLayout()
        layout.addWidget(QLabel("Plugin1 – Tab A"))
        layout.addWidget(QLineEdit("Feld A1"))
        layout.addWidget(QLineEdit("Feld A2"))
        self.setLayout(layout)