Each of the core apps in G-Suite are designed with the basic features most people use often. But Google has built in the ability for others to customize and enhance the functionality of each app through Addons. These Addons are app specific, so you will need to connect your desired addons in each app you want to use it in. Some of these addons provide the ability to link functions of two different apps like creating a customized letter based on information in a spreadsheet. I have chosen several addons that I have used and find very beneficial. Take the time to evaluate them for yourself.
Addons are found within the link in the app itself.
To get to Addons in GMail click the settings (gear) icon and drop down to get addons. Most of the Addons are designed more for businesses in this group of addons, but here are a few that I have used in the past.
WiseStamp
Zoom
Trello
Docusign
Publicate
EasyBib
Docutube
Grackle Docs
Autocrat
Grackle Sheets
Glide Apps Not really an addon. Allows you to create an app from a Google Sheet. Might be a great option to help with contact info while on a field trip.
Grackle Slides
Form Limiter
Choice Eliminator
Form Ranger
Currently Addons are not available for Sites and I don't know that they ever will be due to the nature of Sites and the ability to add various items through docs, embedded html, images, etc.
Currently classroom does not have the ability to install addons. Those would be handled in the other apps associated with Classroom. Should this feature be added, valuable addons will be posted here.