The gform_currency_disabled filter enables or disables the currency drop down on the settings page in Gravity Forms.
Usage
add_filter('gform_currency_disabled', 'your_custom_function');
function your_custom_function($is_disabled) {
    // your custom code here
    return $is_disabled;
}
Parameters
- $is_disabled (string): Value to be filtered. Use “true” to disable the currency drop down. Use “false” to enable it.
 
More information
See Gravity Forms Docs: gform_currency_disabled
Examples
Disable the currency drop down
Disables the currency drop down in the settings page.
add_filter('gform_currency_disabled', '__return_true');
Enable the currency drop down
Enables the currency drop down in the settings page.
add_filter('gform_currency_disabled', '__return_false');
Enable the currency drop down for specific user roles
Enables the currency drop down in the settings page only for users with the ‘administrator’ role.
add_filter('gform_currency_disabled', 'enable_currency_for_admins');
function enable_currency_for_admins($is_disabled) {
    if (current_user_can('administrator')) {
        return false;
    }
    return $is_disabled;
}
Disable the currency drop down based on a custom condition
Disables the currency drop down in the settings page if a custom condition is met.
add_filter('gform_currency_disabled', 'disable_currency_based_on_condition');
function disable_currency_based_on_condition($is_disabled) {
    $custom_condition = true; // Replace with your custom condition.
    if ($custom_condition) {
        return true;
    }
    return $is_disabled;
}
Enable the currency drop down based on a custom condition
Enables the currency drop down in the settings page if a custom condition is met.
add_filter('gform_currency_disabled', 'enable_currency_based_on_condition');
function enable_currency_based_on_condition($is_disabled) {
    $custom_condition = true; // Replace with your custom condition.
    if ($custom_condition) {
        return false;
    }
    return $is_disabled;
}