Hi,

Please refer to the code:

<record model="ir.actions.act_window" id="model_user_new">

    <field name="name">model.user.new</field>

    <field name="res_model">model.user.new</field>

    <field name="view_mode">tree,form</field>

    <field name="context">{'user_new_option': user.user_new_option}</field>

</record>

Hope it helps.

You can set the default value of field just need to add "default_" before the field like like default_user_new_option.

You can write code like below : 

<record model="ir.actions.act_window" id="model_user_new">
  ​<field name="name">model.user.new</field>
  ​<field name="res_model">model.user.new</field>
​<field name="view_mode">tree,form</field>
  ​<field name="context">{'default_user_new_option': uid}</field> </record> 

How to set a default value for a field when creating a new record using the context?

Here's how it's done:

<record model="ir.actions.act_window" id="model_user_new">
    <field name="name">model.user.new</field>
    <field name="res_model">model.user.new</field>
    <field name="view_mode">tree,form</field>
    <field name="context">{'default_user_new_option': 123}</field>
</record>