Extracting the same custom field accross individual custom logs -> 'Custom field with this name already exists'

I'm collecting file logs from two different applications. I have 2 custom logs defined in Azure Log Analytics:

  • CustomLog1_CL
  • CustomLog2_CL

A sample message from both of these:

  • 2018-11-07 14:04:24.878 | 1 | Information | Caller.Type | some message logged from the application
  • 2018-11-08 07:30:00,002 [Thread] INFO Caller.Type - some other message logged from the application

I'd like to create/use the same custom field in both of these:

  • SeverityLevel_CF

However after extracting the SeverityLevel_CF field from CustomLog1_CL ( = Information), I can no longer extract the same field from CustomLog2_CL ( = INFO). Because of the message Custom field with this name already exists

You can also see that I'm met with the same issue on CallerType_CF custom field and CustomMessage_CF.

I'd like the name of this fields to be the same so that I can reuse the same search queries to aggregate logs by CallerType_CF, SeverityLevel_CF, CustomMessage_CF only iterating over different types of custom logs.

Can I achieve anything as such?