Need help with this one....  I normally have multiple floating synth property windows open at the same time, but suddenly now I only get one at a time.  When I try to open a new synth's property window, the existing one disappears and the new one appears.  Is there a setting for this that I accidently changed somewhere? (I'm using version 21.11.00 Build 25 Lexington- x64).  Never had this happen before...

 
Preferences -> VST Settings -> "General" - Recycle Plug-in Windows     <uncheck>
 

thanks, that worked.

You can also "pin" them when they are open, by clicking the push pin icon on the corner of the softwynth's window and then it will stay open. This would be if you don't always want to have your synths open on the screen at once, and gives you some flexibility as to which ones are visible at all times and which ones are not.