Enable Inline

see: <tree>

   <tree editable="1" edit="1">
      <field name="date" />
      <field name="project_id" required="1" />
      ...
      <field name="user_id" invisible="1" />
   </tree>

Disable Inline

see: <tree>

   <tree>
      <field name="date" />
      <field name="project_id" required="1" />
      ...
      <field name="user_id" invisible="1" />
   </tree>