To modify php ini parameters in our domain we must log in to Plesk and go to domains > click on the domain > php configuration:

When accessing, we will have different options to change the values, such as memory_limit, execution_time, upload_max_filesize...:

We must change the value of the parameters to what we want and click accept, below we also have a white box where we can add other php parameters and modify them (it is in the same previous image but at the bottom):

In the example we have put a value of max_input_vars = 100000 like many others can be put, from here many parameters of the php.ini are modified without having to do it by console.

Finally, it is important to check that the changes have been made correctly and the values we have set have been updated, for this, in the same php configuration menu that we are in at the beginning, there is an option called View phpinfo() page, we must click on it and it will take us to the configured values in the php ini of the domain:

This screen or a similar one will appear:

When we enter there, we can see all the values that we have configured, for example, we search by doing a ctrl + f in our browser to find the value of max_input_vars and see if it really coincides with what we have configured:

And that's how we can see it but with the value we want.