diff --git a/project_task_line/__manifest__.py b/project_task_line/__manifest__.py
index b9ab9cac..306dba71 100644
--- a/project_task_line/__manifest__.py
+++ b/project_task_line/__manifest__.py
@@ -1,6 +1,6 @@
 {
     'name': 'Project Task Lines',
-    'version': '14.0.1.0.0',
+    'version': '15.0.1.0.0',
     'author': 'Hibou Corp. <hello@hibou.io>',
     'website': 'https://hibou.io/',
     'license': 'AGPL-3',
diff --git a/project_task_line/models/project.py b/project_task_line/models/project.py
index d0170a57..91c1534f 100644
--- a/project_task_line/models/project.py
+++ b/project_task_line/models/project.py
@@ -7,14 +7,30 @@ class ProjectTask(models.Model):
     line_ids = fields.One2many('project.task.line', 'task_id', string='Todo List')
     subtask_count_done = fields.Integer(compute='_compute_subtask_count', string="Sub-task Done count")
 
+    @api.depends('child_ids')
     def _compute_subtask_count(self):
         for task in self:
-            task.subtask_count = self.search_count([('id', 'child_of', task.id), ('id', '!=', task.id)])
-            if task.subtask_count:
-                task.subtask_count_done = self.search_count([('id', 'child_of', task.id), ('id', '!=', task.id),
-                                                             ('stage_id.fold', '=', True)])
-            else:
-                task.subtask_count_done = 0
+            subtasks = task._get_all_subtasks()
+            task.subtask_count = len(subtasks)
+            task.subtask_count_done = len(subtasks.filtered(lambda t: t.stage_id.is_closed))
+    
+    def action_subtask(self):
+        action = self.env.ref('project.action_view_all_task').read()[0]
+
+        # display all subtasks of current task
+        action['domain'] = [('id', 'child_of', self.id), ('id', '!=', self.id)]
+
+        ctx = dict(self.env.context)
+        ctx = {k: v for k, v in ctx.items() if not k.startswith('search_default_')}
+        ctx.update({
+            'default_name': self.env.context.get('name', self.name) + ':',
+            'default_parent_id': self.id,  # will give default subtask field in `default_get`
+            'default_company_id': self.env.company.id,
+        })
+
+        action['context'] = ctx
+
+        return action
 
 
 class ProjectTaskLine(models.Model):
diff --git a/project_task_line/views/project_views.xml b/project_task_line/views/project_views.xml
index bf255704..c7614426 100644
--- a/project_task_line/views/project_views.xml
+++ b/project_task_line/views/project_views.xml
@@ -5,11 +5,11 @@
         <field name="model">project.task</field>
         <field name="inherit_id" ref="project.view_task_form2" />
         <field name="arch" type="xml">
-            <xpath expr="//field[@name='subtask_count']" position="replace">
-                <div class="o_field_widget o_stat_info">
+            <xpath expr="//div[@name='button_box']" position="inside">
+                <button name="action_subtask" type="object" class="oe_stat_button" icon="fa-tasks" attrs="{'invisible' : ['|', ('allow_subtasks', '=', False), ('id', '=', False)]}" context="{'default_user_ids': user_ids, 'default_parent_id': id, 'default_project_id': project_id}">
                     <span class="o_stat_value"><field name="subtask_count_done" widget="statinfo" nolabel="1"/> / <field name="subtask_count" widget="statinfo" nolabel="1"/></span>
                     <span class="o_stat_text">Sub-Tasks</span>
-                </div>
+                </button>
             </xpath>
             <xpath expr="//page[@name='description_page']" position="after">
                 <page name="task_lines" string="Todo List">