Of course you can manually collapse pallets now, but its seems like what you want is a solo mode feature similar to the one in Lightroom and some other software. This feature is already on DXO’s development roadmap.
Personally, I’m not convinced that a Solo-mode feature (that would collapse the current tool when a new tool is activated, and so on) would suit my way of working … I find I am now very effective and efficient using a customised palette layout that’s exactly suited to the tools and priorities of the workflow I have established over time.
Therefore, as always, I strongly advocate providing an option to switch such features ON/OFF, according to personal preference.
You can have the best of both worlds. If solo mode is implemented correctly we will be able to choose which palettes are controlled by it and which will stay open until you manually close them. I may even divide some of my larger palettes into smaller logical ones to take advantage of the solo feature. I’m guessing that you don’t need to keep everything open all the time. It certainly will reduce clutter.