Code:
menu_item :main :Plato :kfmon :plato.png
generator :main :kfmon
The explicit Plato entry is redundant, the kfmon generator will take care of it (assuming you've got Plato registered in KFMon itself).
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Other than that, the kfmon generator should now pick up UMR's KFMon config, and Bob's your uncle.
It's unclear to me in your last message whether it launches properly or not? If it doesn't, check the KFMon logs, and try launching UMR via the UMR "book" directly (not that it should make any difference).