A lot of applications allow you to see the password you typed in on demand, often requiring you to click on an "eye" symbol or similar. This would also be helpful for the staff interface to help people check for typos when trying to log into Koha.
*** Bug 29247 has been marked as a duplicate of this bug. ***
I've implemented this for the OPAC (at the request of one of my libraries) at bug 34778 Happy for someone to adapt it here as well.