Some parent windows are still accessible even if there are some child dialogs opened.
I’m not sure if I caused it or it was normal for this windows to behave like it. Some Dolphin dialogs work ‘as expected’, like when confirming emptying the trash, or error popups, except settings dialog.
Dolhpin settings dialog:
Chromium save page dialog (I can click, but not type):
Not all dialog windows inhibit interactions with other windows, parent or not, and i can’t say there is an absolute rule for that on KDE Plasma, but maybe you can create such rule via Windows Rules > and set Focus protection or something …
As a rule of thumb, AFAIK only dialogs prevent interaction in the parent window. In some cases, file pickers also do.
Then it’s on per application basis, but many applications that prevent interaction on Windows do not on Linux.