Hi,
either I do not understand the problem correctly or it is related to another problem. The service for memory checks is called “Memory” both on Linux and Windows. Also, on both check plugins we introduced (edit: in v2.0.0) the metric “mem_used_percent” which should be used in your screenshot.
I know, I am a little late in the process - but could you give me some more insights as I cannot reproduce the problem?