If you want to hide the Favorites dropdown menu which showing beside "Group By" dropdown menu, you need to override the owl xml template is below:

In you custom addon, you will add the favorites_menu.xml any your custom addon and its prefer to be added in the following path static/src/xml/favorites_menu.xml and then add the below code to this created file:

<templates>
    <t t-name="FavoriteMenu" t-inherit="web.FavoriteMenu" t-inherit-mode="extension" owl="1">
        <xpath expr="//Dropdown" position="replace">
            <Dropdown class="'o_favorite_menu btn-group'" togglerClass="'btn btn-light'">
                <t t-set-slot="toggler">

                </t>
            </Dropdown>
        </xpath>
    </t>
</templates>
                                  
Then add the below lines in your custom addon manifest file and replace YOUR_MODULE_NAME with you custom addon name:

    'assets': {
        'web.assets_backend': [
            'YOUR_MODULE_NAME/static/src/xml/favorites_menu.xml',
        ]

    },