Is there any way to configure which workspace an application starts at?
I used KDE in the past and we had a feature to configure that, i wonder if there is such functionality or package for XFCE also?
I don’t know if there is a XFCE default option to do that, but devilspie2 works perfect with XFCE
I think it is in the repo also, cannot check because I am at work.
Thanks it seems there is a devilspie2 in the AUR, but as long as we need to write scripts for the functionality needed i might as well use wmctrl… 
Both will do what you want, did not think of wmctrl because devilspie2 is more powerful to manipulate windows.
I’m hoping for some solution that uses a menu when you right click the window-header like in KDE.
Did I misunderstood the question?
Do you want a application to auto open on a specific workspace (as I understood your initial question is) or do you like in KDE want an option that when you right click you can move the application to another workspace?
If the later is the case, then this should be possible if you did setup a few workspaces in the settings. Right click on the application bar should show an option “move to another workspace” for as far I know.
Else you could always set shortkeys in Window Manager>Keyboard. I thought the default was Alt + Ctrl + numpadkey N where N is 1-9 depending on how many workspaces you have.
What i really would like is an option in the title bar’s menu (like in KDE), to configure on what workspace that application/window should (automatically) open in the future.
I think that menu was called something similar to “Advanced window settings”.
Ahh oke.
No there is no default option for that.
Since that is a kwin option perhaps this can help to get what you want.