we need to graph the MIB variable 126.96.36.199.188.8.131.52.184.108.40.206.1.7 (cbQosCMPrePolicyBitRate) but expressed in % in HUM.
We know that it's not possible to make calculations in HUM, what I'd like to know is if there is any other MIB variable that measures exactly this % value.
I've been looking for it but I haven't found anything so any help would be wellcomed.
I will not say that something is "harmless." Bugs can always exist, and certainly this is not the place for a formal bug scrub. However, I have seen no cases where configuring expressions has resulted in a crash. We even have an EEM solution for auto-configuring the EXPRESSION-MIB, so we have been working that MIB out a bit internally with no ill effects.
But if you are worried (and a little paranoia is good), then I highly recommend you test your desired config out in a lab first to make sure what you want to do is safe for your environment.
I don't know of any existing object that would do what you want, but it may be possible to use the EXPRESSION-MIB to create a custom MIB object that gives you the percentage. Here's a tech tip that details how to configure the EXPRESSION-MIB. It assumes the older, ciscoExperiment version which should be supported on most devices unless they are running really new code: