Qt Creator toolbar doesn't appear

I am using Gnome3 as my window manager as well and This workaround worked for me

sudo apt-get remove appmenu-qt5

Souce : Link to bug report with the workaround

Do let me know if this works for you.

On Ubuntu 16.04, I used

export QT_QPA_PLATFORMTHEME=

and restarted Qt Creator.

If you use KDE. Try configure KDE. In menu: System Settings > Application Style > Window Decorations > Buttons add Application menu to Title bar. After it, in Qt Creator must appear button with File, Edit, Build.. menu.