Customer settings such as login settings, customers limits in search, statistics graphs settings, etc. can be configured in Config → Main → Customers:

The page is split into two tabs. The General tab holds the customer settings (login, password, notifications, and more). The Fields tab arranges the layout of the customer form fields:

The General tab contains the customer configuration settings below.
Control how customer logins are generated and changed, and enable two-factor authentication for the Customer Portal.

Can change login while adding a customer - when this option is enabled, it will be possible to change the login while adding a new customer. When this option is disabled, the login will be generated automatically when adding a new customer.
Can change login while editing a customer - enables/disables the ability to change the login of a customer while editing the customers profile.
Characters available when generating a login - add characters which will be used for generating a login (e.g. capital, small letters, numbers).
Show the "Generate" button - enables/disables the option to show the button for generating the customer's login in Customers → Add.
Login format - create a login format. Could be: {id}, {email}, {phone}, {partner_id}, {location_id}, {rand_string}, {rand_number}, {year}, {month}, {day}, etc.
Require two-factor authentication - enable this toggle for two-factor authentication for customers when they log in to the Customer Portal.
If the option is enabled, when the customer enters the correct login and password, they will receive a code via email and/or SMS, depending on their system configuration:

For the correct operation of two-factor authentication, you need to configure email and/or SMS sending.
Type of two-factor authentication (2FA) - choose a two-factor authentication method: Email, SMS, or Email + SMS.
Template for email message of two-factor authentication (2FA) - choose an email message template for two-factor authentication.
Text for SMS message of two-factor authentication (2FA) - choose an SMS text template for two-factor authentication.
Define the characters and length used when generating customer passwords.

Characters available when generating a password - add characters which will be used for generating a password (e.g., capital, small letters, numbers);
Password length - specify the number of characters to use when generating a password.
Configure general display limits and default options for customers.

Max customers to show - specify the maximum number of customers to show in the list when searching for customers.
Format of statistics graph - specify the desired format for the value presented in the statistics graphs of customers.
Default billing type - specify the default billing type of new customers created.
Limit of additional fields - specify the limit of additional fields to show in the customer main information view. Leaving this field on 0 will display all additional fields.
Release IP/MAC when customer is disabled - when enabled, changing a customer's status to Disabled returns the assigned IPv4/IPv6 addresses to the network and clears the MAC bindings on their internet services. Services that take an IP from a pool (From pool) receive a fresh IP automatically on the next RADIUS authentication after reactivation. Services configured with a specific IP from a network (Need IP) reactivate with an empty IP, which an administrator must re-assign. Customer-entered static IPs are preserved.
Set up automatic welcome messages sent to customers by email or SMS.

Enabled - enables/disables automatic sending of welcome messages to customers;
Type - select the type of message to send the welcome message (email, SMS or email + SMS);
Customer status - select the customer status for sending a welcome message;
Delay in sending notifications - specify the delay in sending the welcome messages;
Email template - select the template to use for email welcome messages;
SMS template - select the template to use for the SMS welcome messages.
Birthday notifications send automated birthday greetings to your customers by email or SMS to help improve loyalty and retention.

Enabled - enables/disables automatic sending of birthday greetings to active customers.
Type - select the type of message to send (email, SMS or email + SMS).
Send at - select the hour of the day at which the greeting is sent (system time zone).
Email template - select the template to use for email birthday greetings.
SMS template - select the template to use for SMS birthday greetings.
Greetings are sent only to active customers who have a date of birth set. Default Birthday greeting email and SMS templates are created automatically during migration to 6.0.
Choose the template used for Comments/To-Dos reminder notifications in the customer profile.

The Fields tab controls how the customer creation and edit forms look for administrators. It is split into two blocks: Default fields and Form fields.

Save to apply.The form is arranged as two columns — Left column and Right column — using the same drag-and-drop layout as leads. Fields here correspond to the main and additional fields defined on the Additional fields page.
Add field - each column has its own Add field button. Clicking it opens the Add field dialog:
Click Add to place the field, or Cancel to close the dialog.

Drag and drop - use the handle on a field to reorder it within a column, or move it between the Left column and Right column.
Each field shows its Customer category (the customer type the field applies to) and its Field type (Main or Additional). The ⋮ menu on a field opens its actions.
Use the refresh button to reset the layout to its current saved state.
On upgrade to 6.0, existing Main fields are moved to the Left column and Additional fields to the Right column, with Number of fields rows shown by default set to 20.