Hi Ghassen,

If you want to add it to the 'Invoice Lines' tab try,

<record id ="view_move_form_charity" model ="ir.ui.view" >
<field name ="name" > account.move.form.charity </field>
<field name ="model" > account.move </field >
<field name ="inherit_id" ref ="account.view_move_form" />
<field name ="arch" type ="xml" >
<xpath expr ="//field[@name='invoice_line_ids']//field[ @name='account_id']" position ="after" >
<field name ='charity_account_move_line_id ' />
<field name ='country_id' />
</xpath>
</field>
</record>
If you want to add it to the ' Journal Items' tab try,

<record id ="view_move_form_charity" model ="ir.ui.view" >
<field name ="name" > account.move.form.charity </field>
<field name ="model" > account.move </field >
<field name ="inherit_id" ref ="account.view_move_form" />
<field name ="arch" type ="xml" >
<xpath expr ="//field[@name='line_ids']//field[ @name='account_id']" position ="after" >
<field name ='charity_account_move_line_id ' />
<field name ='country_id' />
</xpath>
</field>
</record>

Hope it helps, 
Kiran K
 ​

<record id="view_move_line_tree" model="ir.ui.view">
<field name="name">view.move.line.tree.chaity</field>
<field name="model">account.move.line</field>
<field name="inherit_id" ref="account.view_move_line_tree"/>
<field name="arch" type="xml">
<xpath expr="//field[@name='name']" position='after'>
<field name="charity_account_move_line_id"/>
</xpath>
</field>
</record>