No HRM Tri connect to Garmin Connect app? Just HRM Pro? Why?

The HRM-Pro has both ANT+ and Bluetooth. The Bluetooth connectivity allows it to connect directly to Android or iOS/iPadOS devices and by extension to Garmin Connect Mobile.

The HRM-Tri is ANT+ only so cannot connect directly to Android or iOS/iPadOS devices and is therefore not visible to Garmin Connect Mobile.

Many Adnroid devices support ANT+. So I suppose this is not a valid reason..

Only HRM-PRO is designed as an independent device. The older HRM models need a Garmin watch - they were not designed to connect to the GC Mobile app directly. They simply do not have the capability (beause of the device design).

Does not feel good that you have to manually put trill HRM Tri in all its activities. Even too bad Garmin does not have a ready-made icon to use. Only this:

Have you added the HRM-Tri as a gear? And now you add it to every activity as a used gear? The icon is the icon for "Other" gear. That is why there is no better icon. 

That is not what that function is for even though you can use it like that. I don't really understand why you want that logged but if you find that interesting it is up to you.

If you want it to be added automatically to all activities you can check the boxes in the settings for the gear.

Than you to learn me how to added automatically. Yes I want to have a icon when use my Garmin HRM Tri. If they can make the gear I think is not difficult to make an icon.

What you really are asking for is the possibility to configure the icons for the gear instead of just using the standard four icons. Garmin Connect can't know that you've added a HRM Tri as gear and use a different icon automatically.

Why do you want to track the number of kilometers you've used the HRM Tri?

Not track, compare history. My Garmins FR245/F6P shows strange data on heartrate I think but must compare over long time.