In the "In Tray" the 'Delete' button is next to the 'Enlarge' button. (Desktop version.)
It is too easy to press the Delete button by mistake, and there is no way to recover the deleted document.
The Delete button should be well away from the other commonly used buttons, so as to minimise the chance of pressing it accidentally.
It would also be better if the deleted documents could be recovered within some period of time 9even if just till you log out of the client).