It is generally possible to transfer Dutch vested benefits to a Swiss pension fund or vested benefits foundation. You have to be employed in Switzerland for at least 5 years before the transfer in order for the benefits to be exempted from Dutch taxes. The transfer is tax-neutral, meaning you won't pay Swiss income tax on the incoming money because it is going to the pension fund or foundation and not to you. You also won't pay Swiss wealth tax as long as it stays in the pension fund or vested benefits foundation.
One important thing to consider is that voluntary payments into a Swiss pension fund generally can't be withdrawn to buy a house until after 3 years from the time they are made. Check with your pension fund whether the transfer would be considered a voluntary purchase of pension benefits. If it is (as I imagine it is) you may still be able to pledge these benefits to indirectly amortize a mortgage. If you are planning to retire in 2021, then the question would be more: does the Swiss pension fund let you withdraw these benefits as a lump sum when you retire or do they have to stay in the fund in exchange for a pension? Most Swiss pension funds let you withdraw voluntary benefits as a lump sum when you retire, so this shouldn't be a problem, but it is worth checking to be safe.
If you plan to buy a house in Switzerland, the main consideration is whether the Dutch or Swiss capital withdrawal tax is lower. In Switzerland, the amount of capital withdrawal tax you pay when you withdraw pension benefits depends on which canton you are tax resident in. This is true for early withdrawals to buy a property, or for regular withdrawals when you retire. Ticino's tax rate is on the higher average end. The tax rate is most relevant for large benefit withdrawals (say, 500,000 francs or more). Below that the difference would generally be a few thousand francs more or less (not enough incentive to relocate).
