There are some suggestions here, but nothing user friendly yet afaik.
In DeltaTouch, click on the header of the chatlist (e.g., your avatar or username). This should open the account switcher. Swipe the entry of your account to the left and click on the “edit” icon. This should open a page that says “Login” and contains your password.
In the official Android app, it’s in Settings → Advanced → Password and Account.