6 nights in Spain

Stay 3 nights in Madrid take a long day trip to Segovia and El Escorial https://el-escorial.com/
(if you have a car).
Train to Toledo
Stay 2 nights in Toledo.
Train back to Madrid

Or, just stay in Madrid and take day trips to Toledo and Segovia. With 6 days, Jazz+Travels idea is a good one since you’d be able to enjoy Toledo after the day trippers leave. Our last 2 trips there we stayed at Hotel Maria Cristina, but you may want one right in the historic center.

Or, given the time of year (Madrid and Toledo aren't exactly toasty in mid-winter), you might head straight to Seville and Cordoba (in either order). Seville's average February temperatures are about 15 degrees (F) higher than Madrid's, and Cordoba is almost as warm.

Although the temperature along the coast in Valencia would probably be pleasant, to me that city ranks way behind the likes of Seville, Cordoba, Granada and Toledo. It's very pleasant, but if you haven't been to the others, I would not choose Valencia.

Unfortunately, I don't see any flights from Seville to Casablanca, but rather to Fes, Marrakesh and Rabat (maybe other Morocccan destinations as well). The Rabat airport's about 70 miles from Casablanca. It's RyanAir that flies that route, so read the fine print exceptionally carefully.

Thank you for your suggestions. They all sound like good ideas and especially the warmer weather in Sevilla and Cordova. What do you think of 2 nights each in Madrid, Cordova then Sevilla? We may have to then fly to Madrid and connect to Casablanca.

Definitely recommend Granada and also the Old Town section of Marbella.

You may already have your flight to Casablanca booked, but it not, I will share what we did (5-6 years ago):

We flew from Malaga to Casablanca on Royal Air Maroc.

We originally booked a 4-leg journey with Delta (with the exception of an internal flight from Barcelona to Granada). Seems it was hours later we got a call from a supervisor at Delta telling us they would be cancelling our Royal Air Maroc booking and suggested we book direct with them. Huh? I asked why.

Apparently Delta was concerned that if Royal Air Maroc changed their schedule, by time Delta was notified to then turn around and notify us, it would likely be too late to get the news to us. Okay...made sense.

But, here is what else was interesting: Delta had told us that we needed to be sure to have the original credit card with which we booked our flight with us when we checked in....or, I could go in person to our local airport to present it ahead of time and have a note made in our record. Huh,I asked? Fraud issues.....I pointed out that I was booking months and months ahead and that if the credit card were fraudulent, they would be able to cancel my flight long before flight day. Apparently that was not the concern....I sort of understood the concern was more with others booking tickets for other people....we were booking for ourselves.....the whole thing was weird, but I am sure the airline had some real fraud and/or security concerns with tickets to/fro Morocco or they would not have put in place such (what we considered) somewhat extreme requirements. . Anyway, even after presenting the credit card at the Delta Counter at the airport months earlier, being assured a note was made in the booking that I had done so, as a back-up I still stuck the credit card with my passport,so as to not forget it (even though it was then expired and replace with one with the different card number). Turns out it was a good thing I had that old card at check-in or we would have been denied boarding. They told me even their super-duper platinum, diamond encrusted level mileage customers had been denied boarding for not having such cards with them, if Morocco was part of their journey.

So,with that long explanation of what we had to go thru, be sure to ask whichever airline you select if there are ANY issues whatsoever that might be similar with your airline. Again, this was 5 or more years ago, and maybe things are different with Delta and Morocco now.

Two nights is way too short for Seville, and it's farther away than Cordoba, so I'd hate to go the extra distance for such a truncated visit. I'd prefer:

4 nights in Madrid with a day-trip to Toledo and 2 nights in Cordoba.

OR

2 nights in Madrid and 4 nights in Seville with a most-of-the-day stop in Cordoba either going to or returning from Seville. There are luggage lockers and/or a left-luggage counter in the bus station across the street from the train station in Cordoba. I can't tell you whether there's a capacity problem, but I don't remember any reports from people who were unable to leave their luggage there.

Mind you, 2 nights in Madrid not really acceptable if you like art and want to go to the three major art museums. Two nights is for folks who aren't interested in art and perhaps just want to see the Palacio Real (which I didn't care for at all, but most people seem to enjoy), the major squares, etc.