Display total maintenance

When there is not enough maintenance (like supply chain failure), there is actually no effective way how to get the estimated maintenance needed to stabilize. Let's add some of all objects' maintenance current status and the same for max.

Not sure if this is the right way to solve it, but maintenance IS a problem at times. Mid-game (T2 and T3) you need a LOT of Maint. for all those vehicles. Many of the T3 buildings are Maint. heavy as well. If you don't keep an eye on it, your Maint. can go from 98+ to 'OMG we're screwed!' pretty quickly and once you hit the Maint. death spiral there's almost no way to recover it.
Perhaps if the buildings 'stored' a certain amount of Maint. based on their cost? That way, you could put a notifier on the Maint. building to alert you when it's maxed out or whatever and you'd still have say 2-3 months of Maint stored in the buildings.