This example is related to the replace menu, but it can easily mapped to the context pad provider.
So your getContextPadEntries can return a function like this
getContextPadEntries(element) {
  /* ... */
  return function(entries) {
    // entries includes all already registered context pad entries
    // remove end event option from entries, for example
   delete entries['append.end-event'];
   return entries;
  }
}
You can find all default entries here.