Thank you for the help Jeremy.  That view is not available in Enterprise V9, but I was able to solve the issue by doing the following:

Turn on Developer Mode > Go to Sales > Leads, Open Lead in Edit view, Click Edit View in the bottom developer tab and

ADD FOLLOWING TO EDIT VIEW IN LEADS FORM:

<group>

<field name="last_activity_id" invisible="1"/>

<label for="next_activity_id"/>

<div>

<div class="o_row">

<field name="next_activity_id" options="{'no_create': True, 'no_open': True}" domain="['|',('team_id','=',False),('team_id','=',team_id)]" on_change="onchange_next_activity_id(next_activity_id)"/>

<span class="oe_form_field" attrs="{'invisible': ['|', ('next_activity_id', '=', False), ('date_action', '=', False)]}"> on </span>

<field name="date_action" attrs="{'invisible': [('next_activity_id', '=', False)]}" placeholder="Choose a date..."/>

<div attrs="{'invisible': ['|', ('last_activity_id', '=', False), ('next_activity_id', '!=', False)]}">

<button name="log_next_activity_1" type="object" class="btn-link" attrs="{'invisible': [('next_activity_1','=',False)]}">

<field name="next_activity_1" readonly="1"/>

</button>

<span attrs="{'invisible': [('next_activity_2','=',False)]}">|</span>

<button name="log_next_activity_2" type="object" class="btn-link" attrs="{'invisible': [('next_activity_2','=',False)]}">

<field name="next_activity_2" readonly="1"/>

</button>

<span attrs="{'invisible': [('next_activity_3','=',False)]}">|</span>

<button name="log_next_activity_3" type="object" class="btn-link" attrs="{'invisible': [('next_activity_3','=',False)]}">

<field name="next_activity_3" readonly="1"/>

</button>

</div>

</div>

<div class="o_row">

<field name="title_action" placeholder="e.g. Discuss proposal" attrs="{'invisible': [('next_activity_id', '=', False)]}"/>

<div attrs="{'invisible': [('next_activity_id', '=', False)]}">

<button name="log_next_activity_done" string="Done" type="object" class="btn-link"/>

<button name="cancel_next_activity" string="Cancel" type="object" class="btn-link"/>

</div>

</div>

</div>

<field name="date_deadline"/>

</group>

To also add this information to the list view for leads, I did the same thing when in the List view:

ADD FOLLOWING TO LIST VIEW FOR LEADS

<field name="next_activity_id"/>

<field name="title_action"/>

<field name="date_action"/>

Hi,

Does registering a next activity send a reminder mail to the concerned sales person?