Hey there
 
I usually have software synths on the right size of screen where the browser is, but now it shows folders instead. How do I make it to show synths? I don't mean the list of synth to insert but already inserted synths?
 
Also where are the settings for software synths? Initially, when I inserted first synth, it had a box opening where I could select simple instrument or MIDI source and 1st audio track and so on. I made my selections and checked "Don't show this again", so not it does not open any more. But I did not check "Open synth rack", so now when I insert synth, it does not open the synth itself.
Thank you.

You can more or less replicate the old behaviour by going Views > Synth Rack View, then drag it to the Browser

The answer to your second question: click the Insert Synth Options button at the top of the Synth Rack. This will open the missing dialog so you can re-enable the "Ask This Every Time" checkbox.

The key binding to toggle display/collapse of the Browser Pane is the letter 'B' on your computer keyboard.  
 
Also here is a link to some documentation on the Insert Soft Synth Dialog Box:
 
https://www.cakewalk.com/Documentation?product=SONAR%20X3&language=3&help=Dialogs2.014.html
 
And, here is the relevant text from the above link - on how to get the Insert Soft Synth Dialog Box to again be displayed every time you insert a new soft synth:
 
"Ask This Every Time
 
If you check this option, this dialog box appears every time you use the Insert > Soft Synths > (name of the synth you want to insert) command, the Insert > ReWire Device > (name of the synth you want to insert) command, or click the Insert button in the Synth Rack view and choose a synth from the pop-up menu. If you always insert soft synths in the same way, you can uncheck this option so you don’t have to deal with the dialog box each time. To open the dialog box when the option is unchecked, click the Insert Soft Synth Options button in the Synth Rack view toolbar."
 
I hope the above helps you
 
Bob Bone
 

Here is one more link that might help you:
 
https://www.cakewalk.com/Documentation?product=SONAR&language=3&help=SoftSynths.04.html
 
It is about working with soft synths and the synth rack, 
 
Bob Bone
 

Thank you.