Hello Malege,
Only a subset of the standard ticket fields are exposed in the decision table to determine SLAs. Out of the 5 category types, only Service and Incident are currently available. On the other hand, all extension fields added to ticket and customer are automatically exposed.
How many Service Levels are you trying to configure? Usually a combination of Service Category, Incident Category, and perhaps a couple of customer fields, is enough to cover any requirement.
Kind regards,
Gabriele Bodda