I have been wondering about this for quite a while and finally thought I would ask.
What is the point of the cutaways page in the symbol library?
The cutaways look like they are intended to be a view 'into' a tank and the most obvious use for this is to show the tank level. However there does not seem to be an easy way to put a bar 'behind' the cutaway so that it only shows through the 'hole'. On reflection, I think I can see why this is not possible: the Background colour would need to show not the bar immediately behind it, but the tank behind that. The fill colour would just need to be transparant as normal.
What actually happens is the Background colour is the only one that can be set and it only has the normal options of specific colours or 'none'. The only way to change the fill colour is to set the cutaway as a multistate.
So it seems cutaways can be used to show the tank content's state (temperature, pressure etc) as a colour but not to show the tank level. Or am I missing something? How are they supposed to be used?