Problem with value inside node (Process variables)

Hello there,

I'm trying to integrate appian with external system and it's working pretty good but I encountered small problem with Process Variables. Description below.

I'm trying to set the value of filed inside my node. When i choose f.g. =pv!dbName everything is fine but when i switch for another field it's disappeared. Can someone help me to figure it out why this field disappeeared afert chaneging field?

Thank you alot,

Dawid :)