Eclipse cubemx plugin falls over
I've seen some other plugins reporting an 'xcb" issue when using OpenJDK
Can you try with an Oracle JVM
On your second point, we are currently implementing the direct project open from STM32CubeMX to SW4STM32.
In STM32CubeMX you'll have a new button Open Project at the end of the code generation that will automatically import or refresh the project into your choosen Eclipse workspace.
Regards
Daniel