Stacking feature is great and seems to work very well.
The ability to choose how many resources from a particular stack to add to the mayor's house is good, but the most common option will be to simply "add all".
An excellent improvement would therefore be to add an "add all" button rather than having to click at the far right end of the resource bar, then clicking OK.
Alternatively, as a simpler solution, the default for how many resources to add should be "all" not "zero", as currently. ie, the resource bar should default to the far right, not the far left.