Just as latest update, we can now develop trigger on some object given above like WorkOrder and WorkOrderLineItem.
I just developed a good workaround to list such items. Even you can use this code to filter out some other types objects (deleteable, searchable...) as well.
Add your org base URL in a remote site setting and run below given code in dev console:
String endpoint = URL.getSalesforceBaseUrl().toExternalForm()+'/services/data/v41.0/sobjects/';
HttpRequest req = new HttpRequest();
endpoint += '';
req.setHeader('Authorization', 'Bearer ' + UserInfo.getSessionID());
req.setHeader('Content-Type', 'application/json');
req.setEndpoint(endpoint);
req.setMethod('GET');
Http httpreq = new Http();
HttpResponse res = httpreq.send(req);
Map<String, Object> m = (Map<String, Object>)JSON.deserializeUntyped(res.getBody());
List<Object> ob = (List<Object>)m.get('sobjects');
string csv = '';
for(Object o : ob){
Map<String, Object> real = (Map<String, Object>)o;
if((Boolean)real.get('triggerable')){
csv+= real.get('name')+',';
}
}
system.debug(csv);