To show your custom fields in the crm.lead list view, you need to inherit the tree view and add your fields.
<record id="crm_lead_tree_view_custom" model="ir.ui.view">

    <field name="name">crm.lead.tree.view.custom</field>

    <field name="model">crm.lead</field>

    <field name="inherit_id" ref="crm.crm_lead_view_tree"/>

    <field name="arch" type="xml">

        <xpath expr="//tree" position="inside">

            <field name="x_custom_field"/>

        </xpath>

    </field>

</record>

Make sure your model extension correctly adds the new fields:
from odoo import models, fields

class CrmLead(models.Model):

    _inherit = 'crm.lead'

    x_custom_field = fields.Integer(string="Another Field")