Persistent BottomSheet below ActionBar

I had the same problem... I don't know if it's the best solution, but for now, worked for me.

Try to put your include inside another CoordinatorLayout in your activity_main.xml, with a marginTop like this:

<android.support.design.widget.CoordinatorLayout
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:attrs="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context="com.test.MainActivity">

    <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:orientation="vertical">

        <android.support.design.widget.AppBarLayout
          android:layout_width="match_parent"
          app:elevation="20dp"
          android:elevation="20dp"
          android:layout_height="?attr/actionBarSize">

          <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            app:elevation="20dp"
            android:elevation="20dp"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"/>
        </android.support.design.widget.AppBarLayout>
    </LinearLayout>

    <android.support.design.widget.CoordinatorLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_marginTop="56dp">
      
      <include layout="@layout/bottom_sheet_additem"/>

    </android.support.design.widget.CoordinatorLayout>

</CoordinatorLayout>

I hope it helps.

We can use app:layout_behavior instead of fixed height

<android.support.design.widget.CoordinatorLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  app:layout_behavior="@string/appbar_scrolling_view_behavior">

  <include layout="@layout/bottom_sheet_additem"/>

</android.support.design.widget.CoordinatorLayout>