Extend with TDTM

This solution utilizes the TDTM framework for all record-triggered automation, so that it can be controlled by the system admin alongside other NPSP automation.

Trigger Handler records can be modified to override/bypass a triggered event while troubleshooting, or to deactivate and replace the event with custom actions.

Extending TDTM

Salesforce documentation: https://help.salesforce.com/s/articleView?id=sfdo.NPSP_Deploy_Apex_TDTM.htm&type=5

Custom handlers should be in the global scope and extend TDTM_Runnable in the npsp namespace.

Example:

global with sharing class CustomSubledgerThings extends npsp.TDTM_Runnable {

    global override npsp.TDTM_Runnable.DmlWrapper run(
        List<SObject> newList,
        List<SObject> oldList,
        npsp.TDTM_Runnable.Action triggerAction,
        Schema.DescribeSObjectResult objResult
    ) {
        // TDTM has a feature to make efficient dml requests
        // Add objects prepped for dml to TDTM_Runnable's DmlWrapper
        npsp.TDTM_Runnable.DmlWrapper dmlWrapper = new npsp.TDTM_Runnable.DmlWrapper();
        // Cast generic sobjects to sobject type
        List<Opportunity> lstOpps = (List<Opportunity>) newList;
        // Route trigger actions
        if (triggerAction == npsp.TDTM_Runnable.Action.AfterUpdate) {
            // Do accounting things
            List<ssfs__Journal_Entry__c> entriesToUpdate = new List<ssfs__Journal_Entry__c>();
            for (Opportunity opp : lstOpps) {
                entriesToUpdate.add(
                    new ssfs__Journal_Entry__c(
                        ssfs__Credit__c = 100,
                        ssfs__GL_Code__c = '1-23-456'
                    )
                );
            }
            dmlWrapper.objectsToUpdate.addAll(
                (List<ssfs__Journal_Entry__c>) entriesToUpdate
            );
        }
        // Return wrapper with added items to update
        return dmlWrapper;
    }

}