Entities in Dynamics 365 contain forms, which display information to the user and can allow input. To view forms of an entity, in customizations, select the entity and Forms:
To create a new form, select New. We will create a new Main Form:
This will open the window:
Note in the form properties we can set the form name:
Make changes to the form, save and publish the form.
Now go to Accounts and select the drop down list. You will see a new form:
Selecting it will display the new form:
If your entity contains multiple main forms, the first main form will be the one and only one displayed in the mobile client.