If by SI prefixes you mean m for milli, k for kilo, M for Mega, etc, then your custom probe will have these automatically inserted to give you optimal representation of these values, in the Range that you create for your custom Probe.
Regarding Your question - I use PicoScope model 3203D for vibration measurement, and I have use PicoScope 6 until now, and I switched to PicoScope 7, so - as there is a very different user interface (which is a great improvement regarding the PS 6 UI) - I am not familiar yet.
I used to take measurement with accelerometers in PS 6, integrate the signal and showing a results in mm/s - which is quite easy to set up in PS 7. This feature is clearly indicated in the Math Channel Set Up window (I like the way it is designed very much). But recently, I have a requirement to measure relative vibrations of shaft where I start using proxy sensors converting voltage get from sensors in um. This requires to set SI prefixes to custom probes, where I looked for the same offer as for Math Channels, but I could not find it there.
I have to say that I bought 3203D in 2015., and I did a lot of measurements since then and I am very satisfied with this piece of equipment. I fulfills most of demands from my side. There are some things that could be a great help if included into firmware/software (I posted some of them already in forum), what I solved as a post-processing analysis with Excel VBA code, so I am fine until now with the might of 3203D and PS6/7. And, If one compares the price/performance ratio of the device, buying your product turned out to be a very good choice. I am very happy that I made that choice. I must add that I have had the pleasure of working with dedicated gear from SKF, B&K, Devesoft (to name a few) - these are premium gears at a premium price. Comfort in usage is guaranteed there. However, with the knowledge of algorithms and theory behind vibration measurement, PS equipment, along with signal post-processing, proved to be a powerful foundation in the field of vibrodiagnostics.
Thanks for the info, and the feedback on our products. I'm glad that you found them to be suitable for your applications in Vibro Diagnostics. That's a testament to the strategy of providing enough methods to customize the operation, control and diagnostics of the tools, for users to be able to tailor custom solutions for their specific application niches, so that they perform at least some of the functions done by dedicated equipment for the field.
I will put in an enhancement request, to our development team, for a function similar to the SI switch in Math Channels.