I made a custom heatmap just like yours (which is helpful) but I'm afraid I'm lost as to how to create an alarm on those metrics.
The heat map correctly shows where there are capacity issues in the guest file system, but I can't get the badges (which alarms depend on) to reflect this.
Porbably missing something simple that I haven't stumbled on yet but it seems like it shouldn't be this hard to create an alarm when a non-C drive is > x %.