Is there any procedure to modify predefined monitors to replace OID if any device doesn't match old one?

I have few Devices of juniper which includes (Juniper M7i Router, SSG140 firewall, J6350 Router) which OIDs either not included in OpManager or not correctly responding in order to display required information.

Also i wanted to create new Infrastructure view device category but i don't want inheritance monitor from predefined category however currently i didn't find any option to create new category without inheritance.

Please help me out and i am ready to share SNMP OID's of devices if you need them.

Please look in attached image to view juniper device stupid display in OpManager even i have created custom monitor which loads graph but doesn't hand shake with predefined (CPU, Mem and Active Conn) graphical look.

Kind regards,
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-OpManager User