Malmo

You should go to Malmberget instead, although that is quite a bit longer away. I'm not sure exactly what "can't walk a lot" actually means, but using a rental car for that trip is a terrible idea. The train is frequent, chep and fast. https://www.oresundstag.se/en/travel-information/accessibility/

Malmö itself is not the most interesting place in that part of Sweden, but there are things to do and see. There is a castle with a museum close to the central station. And the old town centre is in general pretty with a lot of older buildings. As well as some nice parks. And a few churches that can be worth a visit, St Pauli church e.g. And the museum of Modern art.

Thank you for your reply. Please say why taking the bridge is a terrible idea. A family member is very weak and can't walk much so if we took the train how then can we experience the city?

I said that renting a car was a terrible idea, not using the bridge. Both cars and trains use the same bridge. But the bridge toll means it will be a very expensive trip by car, in addition to rental cost, fuel and parking.

Sorry to be blunt, but if you're planning to do this by car, the short answer is that you won't be able to experience the city. The old part I mentioned is more or less car free. And if a family member is weak and can't walk much, the easy answer is in my opinion that they should get a wheelchair.

Thank you for this information. We will take your sage advice!

I did a bit of googling and here are some suggestions for where to rent a wheelchair in Copenhagen. https://www.visitcopenhagen.com/copenhagen/planning/disabled-travellers It seems reasonable.

The trains used across the bridge are wheelchair accessible, they consist of three car units and the middle car is low floor with level boarding.