when in Dorico i minimize the Mixer (via mouse, yellow botton on the frame), there is no way i can bring it up, I need to restart the program to get it back.
Same for the Transport.
On my Mac running OS X 10.3.6, the yellow minimize button does not appear on the Mixer window, so I cannot exactly replicate what you have described. However, you can try the various methods as described in the screenshot I took of the relevant page in the manual. Depending on your keyboard preferences, as set up in System Preferences, you might need to press the ‘fn’ key at the same time as ‘F3’.
yes normally i use the F3 but sometimes i use the mouse to close the window, and accidentally i click the yellow button forcing me to restart Dorico as i havent found a way to bring it up again (i see F3 trigger it but i don’t see the window).
What usually happens when the yellow “minimize” button is clicked is that the window is placed on the dock and then you would be able to re-open it by clicking on its icon in the dock. In your situation, does the window’s icon go down to the dock?
Minimize the main Dorico window and then click its icon in the dock.
Move the main Dorico window around (click and hold the title bar and drag with the mouse) just in case the missing window is hidden behind the main window.