Not that I know of simply because they are different EXE files.
What you can do though is a sort of work around... but it isn't that good and a bit annoying.
Somewhere on your computer, out of the way, create a new folder.
Create a shortcut to both applications.
Right click on an empty part of the taskbar and go to Toolbars
then New toolbar
. Select the location of your folder and choose Select Folder
.
You should now have a group on the taskbar where you can launch both applications from... However, this only deals with launching the applications and doesn't really help your problem - I hope it is better than nothing, but I know of no solution to do exactly what you want.
As for Jumplist, this is simply a feature of the actual application based on what the developer has chosen so maybe you can request a feature.
I just found this by accident: http://www.blogsdna.com/5636/winstack-group-number-of-applications-in-same-icon-on-windows-7-taskbar.htm. It's pretty much exactly what I had in mind. I haven't tried it yet.
– Giscard Biamby – 2009-12-30T13:12:54.070