diff --git a/src/bonsai/bonsai/bim/module/system/operator.py b/src/bonsai/bonsai/bim/module/system/operator.py
index a3554b0dcf..484efb2b6c 100644
--- a/src/bonsai/bonsai/bim/module/system/operator.py
+++ b/src/bonsai/bonsai/bim/module/system/operator.py
@@ -24,6 +24,7 @@ import bonsai.tool as tool
 import bonsai.core.system as core
 import bonsai.bim.helper
 from bonsai.bim.module.system.data import PortData, SystemData
+from typing import TYPE_CHECKING
 
 
 class LoadSystems(bpy.types.Operator):
@@ -51,9 +52,22 @@ class AddSystem(bpy.types.Operator, tool.Ifc.Operator):
     bl_label = "Add System"
     bl_options = {"REGISTER", "UNDO"}
 
+    parent_system_id: bpy.props.IntProperty()  # pyright: ignore[reportRedeclaration]
+
+    if TYPE_CHECKING:
+        parent_system_id: int
+
+    @classmethod
+    def description(cls, context, properties) -> str:
+        if properties.parent_system_id:
+            return "Add new subsystem to the active system."
+        return "Add new IfcSystem."
+
     def _execute(self, context):
         props = tool.System.get_system_props()
-        core.add_system(tool.Ifc, tool.System, ifc_class=props.system_class)
+        ifc_file = tool.Ifc.get()
+        parent_system = None if self.parent_system_id == 0 else ifc_file.by_id(self.parent_system_id)
+        core.add_system(tool.Ifc, tool.System, ifc_class=props.system_class, parent_system=parent_system)
 
 
 class EditSystem(bpy.types.Operator, tool.Ifc.Operator):
diff --git a/src/bonsai/bonsai/bim/module/system/ui.py b/src/bonsai/bonsai/bim/module/system/ui.py
index ab9eda7475..03b4be2af5 100644
--- a/src/bonsai/bonsai/bim/module/system/ui.py
+++ b/src/bonsai/bonsai/bim/module/system/ui.py
@@ -66,6 +66,7 @@ class BIM_PT_systems(Panel):
         if not ObjectSystemData.is_loaded:
             ObjectSystemData.load()
 
+        assert self.layout
         self.props = tool.System.get_system_props()
         active_system_item = self.props.active_system_ui_item
         row = self.layout.row(align=True)
@@ -91,12 +92,15 @@ class BIM_PT_systems(Panel):
         row = self.layout.row(align=True)
         row.label(text="{} Systems Found in Project".format(SystemData.data["total_systems"]), icon="OUTLINER")
         if self.props.is_editing:
+            row.operator("bim.add_system", text="", icon="ADD")
             row.operator("bim.disable_system_editing_ui", text="", icon="CANCEL")
 
             row = self.layout.row(align=True)
             prop_with_search(row, self.props, "system_class", text="")
-            row.operator("bim.add_system", text="", icon="ADD")
             if active_system_item:
+                op = row.operator("bim.add_system", text="", icon="ADD")
+                op.parent_system_id = active_system_item.ifc_definition_id
+
                 system_id = active_system_item.ifc_definition_id
                 op = row.operator("bim.select_system_products", text="", icon="RESTRICT_SELECT_OFF")
                 op.system = system_id
diff --git a/src/bonsai/bonsai/core/system.py b/src/bonsai/bonsai/core/system.py
index 9707c5f6bc..ee35118551 100644
--- a/src/bonsai/bonsai/core/system.py
+++ b/src/bonsai/bonsai/core/system.py
@@ -17,7 +17,7 @@
 # along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
 
 from __future__ import annotations
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING, Optional, Union
 
 if TYPE_CHECKING:
     import bpy
@@ -36,8 +36,15 @@ def disable_system_editing_ui(system: type[tool.System]) -> None:
     system.disable_system_editing_ui()
 
 
-def add_system(ifc: type[tool.Ifc], system: type[tool.System], ifc_class: str) -> None:
-    ifc.run("system.add_system", ifc_class=ifc_class)
+def add_system(
+    ifc: type[tool.Ifc],
+    system: type[tool.System],
+    ifc_class: str,
+    parent_system: Union[ifcopenshell.entity_instance, None],
+) -> None:
+    new_system = ifc.run("system.add_system", ifc_class=ifc_class)
+    if parent_system:
+        ifc.run("group.assign_group", products=[new_system], group=parent_system)
     system.import_systems()