Adding a new flight

Part one:

Unfortunately, you are not allowed to do that because of your stop in Xi'an. As you can see, you cannot use 144 hour visa free transit and have two consecutive stops within mainland China in the same time.

Anyway, I would suggest you to do the following under the assumption that you will return from Beijing to Lisbon using JD429 flight.

Listen now...

This flight departs from Beijing at 20:45 and arrives in Xi'an at 23:00. After that it departs from Xi'an for Lisbon at 01:00 of the next day.

When we know this, and when we know that you cannot use 144 hour visa free transit, you can make your flight from the Philippines through China, eligible for 24 hour visa free transit.

To do that, you will take a flight from the Philippines to Beijing on 22nd of January so that the entire time between your arrival in Beijing and your departure from Xi'an does not exceed 24 hours. There is no particular choice of flights for that particular date, but as I can see, the cheapest would be a flight via Hong Kong by Cathay Pacific. This flight arrives in Beijing at 15:20, allowing you to perform all the formalities with peace of mind until your departure at 20:45.

Part two:

So, if you decide to take this flight, you will approach 24 hour visa free transit counter upon your landing in Beijing where you will apply for a temporary entry permit to be allowed to collect your luggage and also to perform check-in for your flight to Lisbon via Xi'an.

If you decide for this option, you will print out your flight tickets and have those printouts with you. Also, you will declare at check-in in Manila that you will travel to Lisbon via China using 24 hour visa free transit. You will repeat the same thing in Hong Kong if you decide to take this Cathay Pacific flight. Be warned that you should not take a flight from Manila to Beijing via some other mainland Chinese airport because this will disable you from eligibility to use 24 hours visa free transit.

As you can see, the solution is to extend your Philippines trip until January of 22nd and to use 24 hour visa free transit option because you simply cannot use 144 hour visa free transit. I know that this is less convenient, but as you have just one entry, this is your only way to see the Philippines and in the same time to travel via China to Portugal without a visa.