According to the GUI definition of Aseprite, by default the Delete button calls the Clear command. Therefor, you should get a functioning “Delete” button on the On-Screen Controls if you add one that calls it. The code would look like this:
:button{
text="Delete",
onclick=function()
app.command.Clear()
end
}
If you encounter any issues, or need some assistance feel free to let me know ✌️