You can get to Algeciras directly by rail from Madrid for the ferry to Africa. It is certainly possible to do that in a day.
I guess those are your options, it is up to you if you prefer speed or cost.
Cheapest would be an Inner ESpana Ferry-from the 2 ´enclaves, that ES has on he coast here: Ceuta is closest by, as its then inland and not higher priced INTernational. I vaguely remember having once done that-direct bus till border (very strict controls) from Tgr.
The ´Tgr´ ferryport is now also some 30-40 KM east of it and it once even had a 1/day train to it, ONCFM< but this has ceased and its now bus/taxi.
Its not clear from your post if your visit to MArokko is just to Tangier: in fact I would then simply say: skip it. IF you go there, go inland for its atmosfere. Tgr is pretty modern and has all the hassles that tourists can endure and very few on real sights. PLUS that Tgr simply is not a cheap air-port, check RYAN air (or if lucky EASYjet, a far more agreeable airline) to where they fly and what it cost. But 155 for 2, incl some 30-40 for luggage and since 1/1/23 also at least 19€ in EU-taxes is not very unreasonable.
ONce there were indeed direct trenes Mad-Alg, but as the new hi-speed lines are now normal gauge, you change somehwere-probably Bobadilla or close by ; Antequera?(junction north of Malaga).
I however kind of recall that due to many yrs with no maintenance on this rather weak line to Alg. it may be partly under renovation=bustituted-check RENFE.
Alt is paying about 10-12€ for the fast direct BUS from Alg to Malaga and then the AVE=HIspeed tren.
IF you may want to grab this chance to have a peek at this part of ES; Andalucia: why not. F.e. Sevilla is famous for its arab-style old town (can confirm, was there last yr). In fact I would advice that as such MAD is not the most interesting town in ES-its best fame are some good museums.
DO DO read about the always needed RES on RENFE=ES railways that can effectively only be done when there @ counter-and many people report being disappointed due to that at last minute in busy times.
ONce there were indeed direct trenes Mad-Alg, but as the new hi-speed lines are now normal gauge, you change somehwere-probably Bobadilla or close by ; Antequera?(junction north of Malaga).
I however kind of recall that due to many yrs with no maintenance on this rather weak line to Alg. it may be partly under renovation=bustituted-check RENFE.
There still is one daily direct train to Algeciras, but it arrives rather late at night. There are more connections with a switch of trains in Antequera-Sta. Ana, but none allow reaching the 12:00 ferry the author mentions in a different post. They might indeed allow reaching ferries to Ceuta, but from what I've read elsewhere getting from Ceuta to Tangier doesn't seem very straightforward. Haven't done it myself, so no idea.
If this doesn't bring up any results and since this is really outside of the Eurail validity area, you might have more luck on other forums.
I'd forgotten something:
There is a ferry from (Sète in France and) Barcelona to Tanger Med. It takes 29h30 from Barcelona: you could leave Barcelona on the 21st of April at 10:15 and reach Tanger Med. the next day at 14:45. Two persons in a private cabin seems to cost (by booking now) €209.70. Operated by GNV.
You can get to Algeciras directly by rail from Madrid for the ferry to Africa. It is certainly possible to do that in a day.
I guess those are your options, it is up to you if you prefer speed or cost.
Thank you so much @Al_G @Schelte @mcadv :) After I made the post, I found a blog on Seat 61 regarding how to get to Morocco from London-Barcelona-Madrid-Algeciras, which is kind of similar to our route. The post was from 2017 so things might've changes a bit in 2023. 
We are planning to go to Tangier, Fez, and Chefchaoeun. We would like to go to Marrakesh but it is a bit too far and we won't have enough time to go before we have to head back to London. We will spend a couple of nights in Seville before go back to London. I was considering to fly back instead of take several trains for an entire day and try to connect one another. I may have to find a different forum as Morocco is in Africa 
The railway from Madrid to Algeciras is really nice. Especially after Antequera/Bobadilla. Ronda is also worth a stopover.
I’d suggest taking the ferry from Tarifa as you get straigt to Tangier then.
The railway from Madrid to Algeciras is really nice. Especially after Antequera/Bobadilla. Ronda is also worth a stopover.
I’d suggest taking the ferry from Tarifa as you get straigt to Tangier then.
Thank you for the suggestion @MartinM :) If time allows we’ll definitely take the transfer bus to Tarifa then take the ferry cross :)
