Key/Id + Key/number as a system field

Hello API team,

We are current trying to get Key/Id + Key/number to use as our individual identifier for a current integration. Currently we want Key/Id + Key/number it to be (exp, 123456789C0 for company and 123456789C1 for user) as one field instead of 123456789C + 0 and 123456789C + 1 for current and future possible integrations.

Is there a system field inside of Madmax I can query Key/Id + Key/number as one.

Thank you!