I use the Elecom HUGE trackball both in studio and editing office.
I can easily customize the extra Fn buttons in Windows apps. Works fine deleting as requested.
In Audacity, it programs or appears to, but the Fn button (programmed as ‘delete’) does nothing in Audacity.
I’m trying very hard to use my hands w/o having to move unnecessarily to edit audio.
By default, the Delete key on the main part of the keyboard deletes in Audacity, but not the delete key on the numeric key pad.
An alternative default shortcut for deleting is the Backspace key. It may be worth trying programming the Fn button to Backspace to see if that works, as there is only one backspace key.