diff --git a/lizmap/dialogs/main.py b/lizmap/dialogs/main.py
index a5f23261..120a54f5 100644
--- a/lizmap/dialogs/main.py
+++ b/lizmap/dialogs/main.py
@@ -213,6 +213,8 @@ def __init__(
         self.inIgnKey.textChanged.connect(self.check_api_key_address)
         self.inGoogleKey.textChanged.connect(self.check_api_key_address)
 
+        self._ignore_layer_tree_state = False
+
         # Layer tree
         self.layer_tree.headerItem().setText(0, tr('List of layers'))
 
@@ -680,6 +682,7 @@ def follow_map_theme_toggled(self):
     def filter_layer_tree(self, search_text: str):
         """ Filter the layer tree based on search text. """
         search_text = search_text.lower().strip()
+        self._ignore_layer_tree_state = bool(search_text)
 
         def filter_item(item):
             """ Recursively filter tree items. Returns True if item or any child matches. """
diff --git a/lizmap/plugin.py b/lizmap/plugin.py
index 7504b5ce..1d8fcf5e 100644
--- a/lizmap/plugin.py
+++ b/lizmap/plugin.py
@@ -1,4 +1,5 @@
 import contextlib
+import hashlib
 import json
 import logging
 import os
@@ -596,6 +597,9 @@ def write_log_message(message, tag, level):
 
         # Catch user interaction on layer tree and inputs
         self.dlg.layer_tree.itemSelectionChanged.connect(self.from_data_to_ui_for_layer_group)
+        self.dlg.layer_tree.itemExpanded.connect(self._on_layer_tree_group_state_changed)
+        self.dlg.layer_tree.itemCollapsed.connect(self._on_layer_tree_group_state_changed)
+        self.dlg.layer_search_input.textChanged.connect(self._on_layer_search_changed)
 
         self.dlg.scales_warning.set_text(tr(
             "The map is in EPSG:3857 (Google Mercator), only the minimum and maximum scales will be used for the map."
@@ -2489,8 +2493,13 @@ def populate_layer_tree(self) -> dict:
         root = self.project.layerTreeRoot()
 
         # Recursively process layer tree nodes
-        self.process_node(root, None, json_layers)
-        self.dlg.layer_tree.expandAll()
+        self.dlg._ignore_layer_tree_state = True
+        try:
+            self.process_node(root, None, json_layers)
+            self.dlg.layer_tree.expandAll()          # default: all expanded
+            self._restore_layer_tree_group_states()  # override with saved states (if any)
+        finally:
+            self.dlg._ignore_layer_tree_state = False
 
         # Add the self.myDic to the global layerList dictionary
         self.layerList = self.myDic
@@ -2500,6 +2509,66 @@ def populate_layer_tree(self) -> dict:
         # The return is used in tests
         return json_layers
 
+    def _layer_tree_state_key(self) -> str:
+        """Return QgsSettings key for group expand states of the current project."""
+        project_path = self.project.fileName()
+        if not project_path:
+            return ''
+        key_hash = hashlib.sha256(project_path.encode('utf-8')).hexdigest()
+        return f'lizmap/layer_tree_group_states/{key_hash}'
+
+    def _save_layer_tree_group_states(self):
+        """Persist expanded/collapsed state of group items to QgsSettings."""
+        if not self._layer_tree_state_key():
+            return
+        states: dict = {}
+        self._collect_group_states(self.dlg.layer_tree.invisibleRootItem(), states)
+        QgsSettings().setValue(self._layer_tree_state_key(), json.dumps(states))
+
+    def _collect_group_states(self, parent_item: QTreeWidgetItem, states: dict):
+        """Recursively collect expanded state for group items."""
+        for i in range(parent_item.childCount()):
+            item = parent_item.child(i)
+            if item.text(2) == 'group':
+                states[item.text(1)] = item.isExpanded()
+                self._collect_group_states(item, states)
+
+    def _restore_layer_tree_group_states(self):
+        """Restore saved expanded/collapsed state to group items."""
+        key = self._layer_tree_state_key()
+        if not key:
+            return
+        stored = QgsSettings().value(key)
+        if stored is None:
+            return
+        try:
+            states = json.loads(stored)
+        except (json.JSONDecodeError, TypeError):
+            return
+        self._apply_group_states(self.dlg.layer_tree.invisibleRootItem(), states)
+
+    def _apply_group_states(self, parent_item: QTreeWidgetItem, states: dict):
+        """Recursively apply expanded state to group items."""
+        for i in range(parent_item.childCount()):
+            item = parent_item.child(i)
+            if item.text(2) == 'group':
+                group_id = item.text(1)
+                if group_id in states:
+                    item.setExpanded(states[group_id])
+                self._apply_group_states(item, states)
+
+    def _on_layer_tree_group_state_changed(self, item):
+        """Save group states when user manually expands or collapses a group."""
+        if not self.dlg._ignore_layer_tree_state:
+            self._save_layer_tree_group_states()
+
+    def _on_layer_search_changed(self, text: str):
+        """Restore group states when search filter is cleared."""
+        if not text.strip():
+            self.dlg._ignore_layer_tree_state = True
+            self._restore_layer_tree_group_states()
+            self.dlg._ignore_layer_tree_state = False
+
     def from_data_to_ui_for_layer_group(self):
         """ Restore layer/group values into each field when selecting a layer in the tree. """
         # At the beginning, enable all widgets.