The max_input_vars directive can be configured in .htaccess, php.ini, or wp-config.php file. We recommend increasing the default value to 3000. Here is how you can do it:
In .htaccess
php_value max_input_vars 3000
In php.ini
max_input_vars = 3000
In wp-config.php
@ini_set( 'max_input_vars' , 3000 );
Wow! it’s really a helpful article. My theme is asking Max input vars from 1000-2000. Although I have already set 1000 but I forgot how I changed so it’s really what I was looking for. Thank you so much