You can't add an extra day after you've bought a pass and started using it.

If you want to know how much time travel takes, look up the timetables. Do not use the rail planner app for that, since it is very incomplete for Spain and generally does not get enough updates to be reliable. National planners are more reliable (although for Spain, www.raileurope.com works better than RENFE's own website). Also check https://www.seat61.com/Portugal.htm.

For international planning, the DB website or DB Navigator app is good, although it is also incomplete for Spain, since RENFE only shares very little information with the rest of the world.

Best advice is to cut off some expensive over the border TGV/AVE sections (very high supplmt to pay) and use local trains instead. F.e. from Barca to FRance. But as you think-indeed 4days is to little, as only Lisboa->Mad takes afull day if you want to do by train.

Or check WIZZair=the cheap Ryanair for east-eur-often has very affordable flites to these towns. Perhaps from a close by Espana airport. Or if you are really very green thinking: a BUS, f.e. ALSA in ES may also gives shortcuts. Firther on in EUR there are FLIXbus and BlaBla (this one is rather accident prone lately)