There are some ootb Application Settings and you can add your own.
For example: there is already a reference used to configure the base url in your connector rule. Which enables you to create an Application Setting rule on the spot.
However, how does one reference an Application Setting rule in rules such as a datatransform or activity??
Hi @BobReawaruw, I think you’re looking for the datapage: D_pxGetApplicationSettingValue that was introduced in 8.5
Some more information:
Kind regards,
Eric
@Eric Rietveld Thanks! Based on your answer I have found the following video 
Managing Application Settings | Pega Academy
@Eric Rietveld
I’m using v8.4x and don’t have datapage “D_pxGetApplicationSettingValue”. How should I refer the value in the app settings?
Hi @tamont52, a great opportunity to go for an upgrade to 8.5 (or 8.6) I would say. There are also many more enhancements that you can start taking advantage of.
While you’re prepare for this upgrade you could look at the alternative of using a function called getRuleSystemSetting in the meantime. For more information see: https://community.pega.com/knowledgebase/articles/data-management-and-integration/85/utility-functions-global-resource-settings-feature