This is how you can make the Login Form transparent:
1. Add this css to Server Module-> Custom css:
.frmLogin .x-window-body
{
background-color: transparent !important;
}
2. Make the form color in design time to 'clNone'.
3. Form Login->ClientEvents->UniEvents->BeforeInit:
function window.beforeInit(sender, config)
{
config.baseCls='frmLogin';
}
It will make totally transparent with no border, only controls will appear.
I use Extjs 6.5