The wpcrm_system_custom_field_separator filter is used when importing custom fields with one of the import plugins.

By default, this returns a pipe character "|" as the character to separate multiple values for repeater text, repeater textarea, repeater date, and repeater file fields.

Upon import, the plugin will separate each value your import file returns with the pipe character.

However, it may be possible that the value you want to save requires a pipe character, and would cause the import to produce unexpected results.

Therefore, it is possible to change the separator to some other character, or even multiple characters.

For example, use a double pipe character on import:

add_filter( 'wpcrm_system_custom_field_separator', 'my_custom_field_separator' );
function my_custom_field_separator( $separator ){
    return '||';
}