diff --git a/electrum/gui/qt/main_window.py b/electrum/gui/qt/main_window.py
index a34b7f272..279c2ff1f 100644
--- a/electrum/gui/qt/main_window.py
+++ b/electrum/gui/qt/main_window.py
@@ -45,7 +45,7 @@ from PyQt5.QtWidgets import (QMessageBox, QComboBox, QSystemTrayIcon, QTabWidget
                              QVBoxLayout, QGridLayout, QLineEdit,
                              QHBoxLayout, QPushButton, QScrollArea, QTextEdit,
                              QShortcut, QMainWindow, QCompleter, QInputDialog,
-                             QWidget, QSizePolicy, QStatusBar, QToolTip)
+                             QWidget, QSizePolicy, QStatusBar, QToolTip, QDialog)
 
 import electrum
 from electrum import (keystore, ecc, constants, util, bitcoin, commands,
@@ -89,7 +89,7 @@ from .util import (read_QIcon, ColorScheme, text_dialog, icon_path, WaitingDialo
                    CloseButton, HelpButton, MessageBoxMixin, EnterButton,
                    import_meta_gui, export_meta_gui,
                    filename_field, address_field, char_width_in_lineedit, webopen,
-                   TRANSACTION_FILE_EXTENSION_FILTER, MONOSPACE_FONT)
+                   TRANSACTION_FILE_EXTENSION_FILTER_ANY, MONOSPACE_FONT)
 from .util import ButtonsTextEdit
 from .installwizard import WIF_HELP_TEXT
 from .history_list import HistoryList, HistoryModel
@@ -780,13 +780,27 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             self.config.set_key('io_dir', os.path.dirname(fileName), True)
         return fileName
 
-    def getSaveFileName(self, title, filename, filter = ""):
+    def getSaveFileName(self, title, filename, filter="",
+                        *, default_extension: str = None,
+                        default_filter: str = None) -> Optional[str]:
         directory = self.config.get('io_dir', os.path.expanduser('~'))
-        path = os.path.join( directory, filename )
-        fileName, __ = QFileDialog.getSaveFileName(self, title, path, filter)
-        if fileName and directory != os.path.dirname(fileName):
-            self.config.set_key('io_dir', os.path.dirname(fileName), True)
-        return fileName
+        path = os.path.join(directory, filename)
+
+        file_dialog = QFileDialog(self, title, path, filter)
+        file_dialog.setAcceptMode(QFileDialog.AcceptSave)
+        if default_extension:
+            # note: on MacOS, the selected filter's first extension seems to have priority over this...
+            file_dialog.setDefaultSuffix(default_extension)
+        if default_filter:
+            assert default_filter in filter, f"default_filter={default_filter!r} does not appear in filter={filter!r}"
+            file_dialog.selectNameFilter(default_filter)
+        if file_dialog.exec() != QDialog.Accepted:
+            return None
+
+        selected_path = file_dialog.selectedFiles()[0]
+        if selected_path and directory != os.path.dirname(selected_path):
+            self.config.set_key('io_dir', os.path.dirname(selected_path), True)
+        return selected_path
 
     def timer_actions(self):
         self.request_list.refresh_status()
@@ -2509,7 +2523,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
 
     def read_tx_from_file(self) -> Optional[Transaction]:
         fileName = self.getOpenFileName(_("Select your transaction file"),
-                                        TRANSACTION_FILE_EXTENSION_FILTER)
+                                        TRANSACTION_FILE_EXTENSION_FILTER_ANY)
         if not fileName:
             return
         try:
diff --git a/electrum/gui/qt/transaction_dialog.py b/electrum/gui/qt/transaction_dialog.py
index 8be43cf8f..97bd48dd0 100644
--- a/electrum/gui/qt/transaction_dialog.py
+++ b/electrum/gui/qt/transaction_dialog.py
@@ -50,7 +50,9 @@ from electrum.logging import get_logger
 
 from .util import (MessageBoxMixin, read_QIcon, Buttons, icon_path,
                    MONOSPACE_FONT, ColorScheme, ButtonsLineEdit, text_dialog,
-                   char_width_in_lineedit, TRANSACTION_FILE_EXTENSION_FILTER,
+                   char_width_in_lineedit, TRANSACTION_FILE_EXTENSION_FILTER_SEPARATE,
+                   TRANSACTION_FILE_EXTENSION_FILTER_ONLY_COMPLETE_TX,
+                   TRANSACTION_FILE_EXTENSION_FILTER_ONLY_PARTIAL_TX,
                    BlockingWaitingDialog)
 
 from .fee_slider import FeeSlider
@@ -323,12 +325,19 @@ class BaseTxDialog(QDialog, MessageBoxMixin):
         if isinstance(tx, PartialTransaction):
             tx.finalize_psbt()
         if tx.is_complete():
-            name = 'signed_%s.txn' % (tx.txid()[0:8])
+            name = 'signed_%s' % (tx.txid()[0:8])
+            extension = 'txn'
+            default_filter = TRANSACTION_FILE_EXTENSION_FILTER_ONLY_COMPLETE_TX
         else:
-            name = self.wallet.basename() + time.strftime('-%Y%m%d-%H%M.psbt')
+            name = self.wallet.basename() + time.strftime('-%Y%m%d-%H%M')
+            extension = 'psbt'
+            default_filter = TRANSACTION_FILE_EXTENSION_FILTER_ONLY_PARTIAL_TX
+        name = f'{name}.{extension}'
         fileName = self.main_window.getSaveFileName(_("Select where to save your transaction"),
                                                     name,
-                                                    TRANSACTION_FILE_EXTENSION_FILTER)
+                                                    TRANSACTION_FILE_EXTENSION_FILTER_SEPARATE,
+                                                    default_extension=extension,
+                                                    default_filter=default_filter)
         if not fileName:
             return
         if tx.is_complete():  # network tx hex
diff --git a/electrum/gui/qt/util.py b/electrum/gui/qt/util.py
index 2a2278a61..7e32b2103 100644
--- a/electrum/gui/qt/util.py
+++ b/electrum/gui/qt/util.py
@@ -51,7 +51,12 @@ pr_icons = {
 
 
 # filter tx files in QFileDialog:
-TRANSACTION_FILE_EXTENSION_FILTER = "Transaction (*.txn *.psbt);;All files (*)"
+TRANSACTION_FILE_EXTENSION_FILTER_ANY = "Transaction (*.txn *.psbt);;All files (*)"
+TRANSACTION_FILE_EXTENSION_FILTER_ONLY_PARTIAL_TX = "Partial Transaction (*.psbt)"
+TRANSACTION_FILE_EXTENSION_FILTER_ONLY_COMPLETE_TX = "Complete Transaction (*.txn)"
+TRANSACTION_FILE_EXTENSION_FILTER_SEPARATE = (f"{TRANSACTION_FILE_EXTENSION_FILTER_ONLY_PARTIAL_TX};;"
+                                              f"{TRANSACTION_FILE_EXTENSION_FILTER_ONLY_COMPLETE_TX};;"
+                                              f"All files (*)")
 
 
 class EnterButton(QPushButton):