web/web_widget_dropdown_dynamic/readme/USAGE.md

@api.model
def method_name(self):
    values = [
        ('value_a', 'Title A'),
    ]
    if self.env.context.get('depending_on') == True:
        values += [
            ('value_b', 'Title B'),
        ]
    return values

<field
    name="other_field"
/>
<field
    name="char_field"
    widget="dynamic_dropdown"
    options="{'values':'method_name'}"
    context="{'depending_on': other_field}"
/>

DEMO

On User defined filters added new field to show the feature, it is called Dropdown Integer. If any user selected just One option shoud appear, but if Mitchell Admin it should be possible to select option One and Two.