How can the admin's username password, be remembered or added it to the keychain so these annoying prompts would be less frequent?
The app referenced here (Anvil) is not relevant.
I'm looking for a way to loosen up the the prompts for credentials.
You can go about this the other way around.
Open Keychain Access and find the items you need and modify that item so that the app in question is white listed for the password or credential being used.
Once you are in Access Control - you can white list certain apps or all apps. This can be automated if the dialog has an "always remember" or "don't ask again" check mark so that the ACL can be set properly without needing to enter Keychain Access from the back end on a case by case basis.