It happens for me for save project and save as, the dialog doesn't show when chitubox is maximized, alt-tab doesn't work, the only way I found to make it appear is to press control alt delete, then clicking cancel, the dialog is somehow brought back to the front. Windows 10 pro 1903 64 bits
Also tried after upgrading to win 10 1909, same issue.
It started when the software switched to the black theme I think.
The Photon workshop software from anycubic also suffers from the same symptoms also since they switched to a black theme
I see the same effect with Chitubox 18.104.22.168 beta and Windows 10 Home 10.0 - When the Chitubox window is maximized, all file dialogs are hidden and Alt-Tab does not work anymore. Only way to the file dialog is pressing Ctrl-Alt-Del - When Chitubox is not maximized, all file dialogs open correctly in front of Chitubox window - Happens on laptop and laptop+external monitor