Europe suggestions for October--help with my FOMO

None of the places you want to visit are your way to Lisbon. You could take a train from Copenhagen and work your way to PT. Have you considered taking a train that will go through Denmark, Germany, Belgium, France and Spain?
Have you checked to see what nonstop flights operate out of Copenhagen? I see a flight from CPH to Warsaw / Budapest for $38. Split for $75.

I appreciate your prompt reply. Not worried about heading in a particular direction. Just trying to tick off some places on my list. And yes, I always go to Google Flights to make sure I can get to/from a location without a high cost or length of time.

Why not someplace(s)( in France or Spain?

Been all through Germany

Also in the north, on the Baltic Sea or North Sea? In Lübeck, Schwerin, Rostock, Stralsund, or Wismar? To name just a few.
Or east, in the Spreewald or Saxon Switzerland?

None of the places you want to visit are your way to Lisbon.

Budapest is on the way. Wizz and Ryan both fly non-stop Copenhagen to Budapest and then there is non-stop from Budapest on Wizz and Ryan to Lisbon. Both tickets start well under $100 but that all depends on how light you travel.
September is a wonderful time to be here. Almost ideal. A good stay in Budapest is 5 days. But you have 10 days you say. So 2 days of travel in and out of Budapest, 5 days in Budapest (with a day trip to the Danube bend towns) and 3 days in Eger = 10 days.
Favorite Tourism Video of Budapest https://youtu.be/1nd5AtZIrTk?feature=shared
Anthony Bourdain describing how visually pleasurable Budapest is https://youtu.be/0nd9DuDGCz0?si=aa0c19KaJHEtabkX

Krakow is on the way. Ryan does a non-stop from Copenhagen to Krakow. Then there are Ryan flights from Krakow to Lisbon on Tuesday and Saturday. Both tickets start well under $100 but that all depends on how light you travel.
But 10 days is too long for Krakow. Someone else will have to help you fill the ten days.

Krakow and Budapest are on the way. You could fly down to Krakow, spend 3 days then take a night train to Budapest (or fly with a stop in Warsaw). That would give you about 5 full days in Budapest and a total of 10 days.

SEPTEMBER EVENTS in Budapest (still a bit early but there is a thread for updates: https://community.ricksteves.com/travel-forum/hungary/list-of-budapest-events-july-through-october-25)
27th Steam train trip to the Danube Bend https://www.mavrailtours.hu/hu/travels/2025
8 thru 17 (last year’s date, 2025 date not published yet) Jewish Cultural Festival This is good, very good https://www.zsidokulturalisfesztival.hu/
11 – 14 Budapest Wine Festival at the Castle (really, really good) https://aborfesztival.hu/en
18 through 21 (last year’s date) Corvin Beer Festival.

You say you have a list. There you go.

So very much appreciated! Thank you for your generous advice.

Fly to Krakow, train to Warsaw, fly to Budapest. :) Or just do 2 of the 3. There’s plenty to see and do in any two of those cities to fill your 10 days.

That sounds like a winning plan, thank you.

TexasTravelMom, I overlooked an option LOL.

The OP can do a lot with 10 days and the flow to Lisbon works with any of the choices.

From Budapest I was thinking I might visit Timisoara or Bratislava. And would hiking in Cinque Terra be rainy and still full of tourists?

We’ve never been to Poland, but will be heading for there in less than two weeks. Using the recommendations from Rick Steves’ guidebook, we’ve booked a driver to get us to Auschwitz from Krakow and back, although if we’d stayed in Katowice, we’d be closer to Auschwitz for that day. As for FOMO, we still have about a week without definite plans for where we’ll go and stay, and need to pick spots. There are several interesting cities and towns in western Poland, some in the southeast, and some remote places in the northeast, near national parks. Rick’s Big Three destinations of Krakow, Warsaw, and Gdańsk are on the itinerary, along with fourth suggestion Toruń, but from there, we still have time for 2 or even 3 more, and need to decide.

We first went to the Cinque Terre in 2001, just before 9/11. Magical. Second time was three years ago, and it was so mobbed that I’ve vowed “never again.” I don’t want to say that if you’ve never been, then don’t go, but I wouldn’t put it at the top of my bucket list when there are so many places that haven’t been overrun, including others on the coasts of Italy.

From Budapest I was thinking I might visit Timisoara or Bratislava.

Interesting choices. Bratislava is a couple hours up the rail line from Budapest. It has a very polished old town that has been extensively developed for tourism. Timisoara is under 6 hours and under $20 on the train. I havent been. But it does sound facinating. But for the time it takes to get there and back I would want to spend a few days and I am not sure its up to that. Still, if i were forced to do one of the other I would do Timisoara as Bratislava just didnt light my fire.

Other ideas Tihany and lake Balaton https://youtu.be/R7ySZkc_LSU?si=sJOGDNs5MPuYTuAB and https://youtu.be/Jwhd8vO0ZO4?si=HtdfpLtDwk919dgh
Győr and Pannonhalma https://youtu.be/9-9pN3gZ0GA?si=8nVBZWjLR9dILb1E and Pannonhalma https://youtu.be/NRJrXvDnTS8?si=oZfXCHRmIsyHVv0T
Lillafüred for the outdoors, caves and little trains. https://youtu.be/N4dDLtjPnUk?si=8sn3TdghTVdJF7MZ and https://youtu.be/pj4EyxKu6vc?si=gODn0zyFl91dvNRz
Pecs for the last mosques in Hungary and great history https://youtu.be/h0mNHUqVfmQ?si=bOueHn3bbja-WV3r

ANd I think the Danube Bend (Szentendre, Esztergom and Visegrad) are every bit as interesting as Bratislava. https://youtu.be/OoDYOsZB3lk?si=LBXFhsbOvoYS5Doa But do it in two or three days, not one.

Thanks for all the generous advice.