Let me caveat my response by saying I don't have experience using a watch with the app.

If the watch displays the same notification actions as shown on the phone, it might be a simple case of enabling the delete button to show on the notifications.

Have a look in the app [settings > general settings > notifications] page. Change "Show delete button" to your desired option 2 or 3.

1. "Never" 2. "For single message notifications" 3. "Always"

In the notification area "show delete button" was set previously "Always" and now is set "for single message notifications". But the option in watch to delete the email is still missing.

On my g-mail app i don't have to do any modification to any settings and the "delete" option is present on my Garmin watch.

Hi Lucian

Thanks for responding.

I suspect development would be required to support your request. You could try creating a ticket on Github and see what feedback the developer's can offer. https://github.com/thunderbird/thunderbird-android/issues

Mozilla Connect is also a great place to promote your suggestion and have it voted by the community. The below idea is a similar topic or you can create your own. https://connect.mozilla.org/t5/ideas/thunderbird-wear-os-version/idi-p/77658