Short answer
A consolidation loan pays off when the new rate is lower than the weighted rate on your current credit and you do not extend the term. The trap is that the monthly cost falls sharply while the total interest cost rises, because the debt is spread over ten years instead of three.
Work out the weighted rate first
If you have SEK 45,000 at 21.9%, SEK 28,000 at 19.5% and SEK 15,000 at 22%, your weighted rate is about 21.2%. A consolidation loan at 12% is then a clear improvement, provided you keep roughly the same repayment time.
Card credit and quick loans near the 22% rate cap are almost always worth paying off. An existing personal loan at 7% rarely is; you risk pulling a cheap loan into a more expensive one.
The term is where the money goes
The same SEK 88,000 debt at 12% costs about SEK 17,000 in interest over three years and just over SEK 60,000 over ten. The monthly cost falls from SEK 2,900 to SEK 1,260, which eases the monthly budget but costs more in total.
Extending the term because you cannot manage the current payments is a legitimate decision. But make it deliberately, and pay extra when you can. A personal loan can always be repaid early, and at a variable rate without a fee.
Check that the old credit is cleared
Some lenders pay off your existing credit directly, others pay the money to you and trust you to do it. The second is where things go wrong: the money lands in your account, some goes elsewhere, and you are left with both old and new loans.
Cancel the credit once it is cleared. A credit card with a zero balance but a SEK 60,000 limit still counts as debt at the next credit assessment.
