Qt designer does not allow to do it, that is the default configuration that plugins have, so I will propose a workaround, modify the .ui with a small script to disable that property:
from PyQt4 import QtCore, QtXml
if __name__ == '__main__':
filename = "/path/of/your_file.ui"
file = QtCore.QFile(filename)
if not file.open(QtCore.QFile.ReadOnly):
sys.exit(-1)
doc = QtXml.QDomDocument()
if not doc.setContent(file):
sys.exit(-1)
file.close()
strings = doc.elementsByTagName("string")
for i in range(strings.count()):
strings.item(i).toElement().setAttribute("notr", "true")
if not file.open(QtCore.QFile.Truncate|QtCore.QFile.WriteOnly):
sys.exit(-1)
xml = doc.toByteArray()
file.write(xml)
file.close()
Note:
The script is compatible with PyQt4, PyQt5, PySide and PySide2, they should only change PyQt4 with the name of the other libraries.