Preferred Sport in list

From your request I can't tell what you are requesting, so perhaps others might not be able to tell either.

Where is it that you get these three options?

Are the activities created by move IQ?

What menus took you there?

What device are you using?

Do you mean the Garmin Connect Mobile app? If so, then you might want to post your request in https://forums.garmin.com/forum/into...ns-ios-android

In Garmin Connect, you get three options when doing a workout - Run, Cycle, Other.

Are you talking about executing a (custom) workout offline, i.e. actually going for a run in a predefined manner, or just creating a workout in Garmin Connect online?

You can also create (pool) swim workouts in Garmin Connect.

Part of this is my long standing request to have the device give you an option of your personal top three sports,

Run, Bike, Pool Swim and Custom are the structured workout types supported in the ecosystem and understood by selected models of Garmin wearable devices.

No point in giving the user an option to specify anything else in a drop-down menu if the system does not support its execution.

but the other part is that the Connect app allows you to change this to another sport after the workout.

Under the Activity, you should be able to see your personal Activity Types first, then the long list of sports that everyone else does.

No, there is no "should". You want customisation that makes it more convenient for your use case, and that's fine, but it's neither feature specified in a technical standard with which Garmin ought to comply, or a service obligation that the company ought to accommodate. There is no inherent entitlement to having the service structure or deliver things on your preferred terms.

This is super annoying as you have to go down a fairly long list that for the most part is un-necessary.

Annoyance is an emotion that entirely up to you to feel or not feel in response, and not for Garmin to manage or avoid.