OK. Once you have laid all the panels out, look at the bottom of the small MAIN panel. You should see ‘save ws’. Click on that and (working from memory here…) you should be given the choice of saving it as the default layout or other. I just click on ‘default’ and over-write whatever is in there. Works for me.
BTW. This forum is no longer run by the SDRPlay team, it’s an independent thing and is very quiet these days. Questions asked here often go for weeks without an answer, so can I suggest you join the Facebook group? If you go back to the main body of the site and click on ‘community’, you’ll find a link there. The FB group is quite busy and questions are answered within minutes.