I downloaded and installed version 10.0.6 as soon as it became available today. My first test was to see if the bug had been fixed where if you add a new FX plug-in on a track it causes previous FX plug-ins added on the track to lose their settings. This bug renders the program unusable for any serious work so I sincerely hoped I was going to find it fixed at long last - but no it is not fixed. Frankly, I think it is an absolute disgrace that the company has left users of their software having to cope with such very serious and basic bugs for so long. These destroy our enjoyment of the program and render it nothing more than a nuisance. I can't tell you how very upset and disappointed I am today. What is wrong with these MAGIX people that they do not understand the responsibility and duty they have towards us, the end users, to give us a properly working program?
Update 24 June 2022
I logged the FX problem with support and received a very prompt reply notifying me that there is a workaround which I was not aware of. To add additional FX plug-ins to a track we can use the Plug in Manager (View/Plug-In Manager) and drag the required plug-in onto the track header. This approach does not impact on the settings of previously applied plug-ins on the track. I have tested this and it works. Many thanks to Ralf in MAGIX Support for this information and to Xoc for a more detailed explanation. (See Xoc's post below.)