I bought my first add-on plane for FSX the other day, a DHC-4 Caribou from Virtavia. The plane is pretty cool and the keyboard controls are exactly the same as for other multi-engine prop jobs, so it makes the transition fairly straightforward.
However, I discovered that this model doesn't have a designated window for the throttle quadrant, so you can't pull up an image of your prop, mixture, and throttle controls. You can still make adjustments to these by keyboard command (which I tend to do anyway since my controller only has a throttle control and not prop/mixture controls).
But one thing I don't seem to be able to find is a way to tell what my current mixture setting is. In some of the default planes in the sim I would pull up the throttle, point to the mixture, and it would pop up a little box to tell me what the setting was (e.g., 31%, 20%, etc.). But without a mixture lever to point to, I can't figure out how to tell what my mixture rate is in the Caribou.
Other than those tool tips, is there any log file or menu option you can check in the sim to tell you what your current mix rate is? I like being able to know what setting to use when I fly at a certain altitude in a certain plane to get the best performance, and without knowing what the mixture rate is, I find myself falling back on those little popup messages warning about the engines losing power due to improper mixture settings, and that gets annoying.