See menu options and click on Database > Change Master Key / Tools > Settings, etc

There is no possibility to access them.

Right Click on Tabbar, Suggest a font. Define settings at keepassxc.ini
I've migrated from an KeePass version 1 database and now KeePassXC warns me about generating a new key file for my DB, but I have no options to do it.
I can't access to Help → About here.
KeePassXC - 2.3.1
Revision: 2.3.1-0ppa1~trusty1 (Ubuntu 14.04)
Libraries:
Operating system: Ubuntu 14.04.5 LTS
CPU architecture: x86_64
Kernel: 3.13.0-145-generic
Enabled extensions:
They are probably in the very top of the desktop display.
You're right, this menu options are shown at Unity desktop top bar, but not at Gnome Flashback desktop (I use this last one)
You probably want to uninstall the appmenu-qt5 package. You can also try playing with the QT_QPA_PLATFORMTHEME env var. Set it to gtk2 to prevent the appmenu from being used.
An interesting read on how Qt5 styles itself:
https://wiki.archlinux.org/index.php/qt
Thank you very very much @droidmonkey!!!!!
This works perfect!!!!!
QT_QPA_PLATFORMTHEME=gtk2 keepassxc
I've added to my aliases file :-)
Most helpful comment
Thank you very very much @droidmonkey!!!!!
This works perfect!!!!!
I've added to my aliases file :-)