Denmark wants to build two energy islands to supply renewable energy to Europe

This is similar to what Germany and to some extent Italy are doing, and it's very different from sanctions. I'm ambivalent.

Germany's clearer, so I'll use it for examples: Germany bought coal, oil and gas from Russia, and decided to stop that after the invasion. This is a big threat to Russia, because it's large, fifty-year-old contracts being ended, and that has a certain finality. Once a customer has found a replacement for a large and old contract, regaining that customer is no simple matter.

Sanctions take effect quickly, but can be ended just as quickly. The Ukrainians can use sanctions for bargaining, "give us Crimea back and we'll ask our friends to cancel their sanctions, so you can get spare parts for your BMWs and supplies for your dentists".

On the other hand, these changes have urgency. So long as the Danes haven't started building, the Russians can hope to repair the relationship. If the Russians wait too long with starting the negotiations, Denmark will have half-constructed new infrastructure. That's not going to be torn down again, once started.

There's something to be said in favour of time pressure. But I'm ambivalent. Thanks for listening.