Hi @Yke80
If you open the 10-day stretch and you apply an 8-day minimum stay to all 10 days, it will effectively mean that a booking can't start on any of the last 7 days. The booking can only start on day 1, 2, or 3. Someone asking for a booking to start on day 4 will not be able to see and book your place, because their stay cannot be 8 days or more. So I think this does actually solve your problem. The risk is that you may not find a guest who specifically wants to make a booking starting on one of the first 3 days. As the dates come nearer, you may need to revise your requirements if the dates don't get booked.
If you want a more advanced solution to your problem, go to your profile in the top right corner and click on "account". Scroll down to professional tools and turn it on. When you use professional tools you can create more complex rule sets to block specific dates from check-ins and check-outs and to set minimum stays. Professional tools are a bit more difficult to work with than the regular calendar, but the tool set does give you some more advanced options.