I'm going to keep on assuming you are using VL 5.9 Gold.
Just guessing because wbarconfig is in the menu of deluxe and its called vlbar and launched from the terminal in light. But if I'm wrong just ignore the following.
So for VL 5.9 here is what you do.
How can I for instance add an icon on the taskbar for a command?
And is there a way to configure WBAR?
1st question, I think your referring to the panel bar and not wbar.
To give you some reference take a look at some of the iconed items in your panel already. The notepad, house, or even the file with the wrench in it. Right click on any one of them and click on properties. These are all launchers. Some can even launch several different things. (One of my favorite things about xfce) You probably already know you can create your own launcher by right clicking on an empty part of the panel -->choosing add new item -->launcher.
Under the Name line and Description line you will see a box with an icon in it. That box has an arrow. When you click the arrow you can select any of those icons given for your launcher.
Not good enough, but wait, there's more.
Click on the folder to the right of that line and navigate to /usr/share/pixmaps/
choose any file of your liking that ends in .png Click open and there you go.
But wait still more...
Use catfish to search the name of the app you've made a launcher for and .png and it will find the icon and the path for you. Just put that info in the line for icon in the launcher properties.
ex. /usr/share/wbar/iconpack/wbar.osx/nautilus.png. Will give you the nautilus.png used by wbar.
Speaking of wbar...
Your configuration file for wbar can be found at /usr/share/wbar/
Open the folder as root or you will not be able to make any changes.
right click on the file called dot.wbar and open with mousepad (or the text editor of your choice)
The first 3 lines are for the bar itself but each set of three after that gives the program the icon location, the launch command, and the text discription.
If you want to take something out just delete it
If you want to add something in follow the same format. Including the i: c: t: they have starting each line.
For example I added appfinder to wbar with this...
Clicked save. Started Wbar and there it was.