It's hard to get specific info out of the d5t5 guys, but the bits and pieces I've picked up is it's all harder than it seems. This isn't like buying VAGCOM and going to town on your Audi. To even make any config changes to your car you need to unlock the CEM and/or the ECM. You are most likely dealing with the CEM. Unlocking the CEM used to be a DIY process that VDash handled by brute force cracking the code you need on older Volvos. On an SPA car, it requires the CEM unit be removed and the flash program on it copied out and then the code is gotten out of that somehow. All VDash says is you need to take it to (1 of 3 in the US) VDash PRO dealers to have this done. There is also a way to sniff the communication when a dealer does an update (likely steal the code sent to unlock the CEM for changes) but I don't know how involved that is or how cozy you need to be with your dealer techs. Or perhaps possible you can subscribe to the top level of VIDA, get the software connected to your car, and purchase a software update yourself and sniff the code, which is possible for US owners to do directly.
Once you clear that hurdle, it seems that there are two types of "configurations": the first is a binary type of enable or changing a feature, like the speed limiter. You just change it and it is done. The second type of change is modifying your car configuration, i.e. you change an "option" so something your car did not originally have, like say B&W stereo, you can change that so the car reports to Volvo it has this option. When you do this you are not quite done yet...you need to either get a software update, or the module you are trying to work on, needs to be reloaded, to get the proper software to do the thing you are trying to do. Those software reloads have to be purchased from Volvo, either pay a dealer or pay for VIDA, get the software working on your laptop and buy the reload and load it. The example of the B&W stereo, there is a thread in the S90 forum, some guys swapped the B&W speakers and amp. They get some of the B&W settings in the Sensus just plugging the amp in, but they don't have some features like the "Gothenburg Hall" and other sound settings. Not until their CEM has been changed to have the B&W option, and then they get a software update or pay for a module reload will that work correctly.
I looked into this when I thought it might not be too bad to add the "high level illumination" feature to my car, so I could swap the door harnesses and plug in the missing various LED units and enjoy. But once I realized I need to remove my CEM, in order to use VDash to change the option, and then pay for 4 reloads of each door module software...just became not worth it.
Every time I see one of these threads talking about changing stuff with VDash, it seems there is someone who is reading the d5t5 website and just reciting from the price list. Killroy do you have actual experience with the process? If I am missing something and it's easier than I am understanding, it would help us all out to clarify!