How to use insert-key in (blue) Bitlocker password dialogue directly after booting

I just encrypted my Framework-Laptop using Bitlocker.
The (blue) Bitlocker-Dialogue appearing after startup and asking for the password offers to press the insert-key to show the entered password.
I know, that insert is located as a secondary usage on the del key, but I am unable to activate it in that dialogue, at least pressing Fn at the same time does not work.
Thanks for any help!