Keyboard modifier-key

hello and thank you for this library. i have an understanding problem with the modifier keys. Letters "print" works without problems but when i try a modifierbutton it doesn't work. is the Keyboard.printf command wrong for this? It should not write KEY_Strg for example but emulate that it is pressed. Thanks in advance.

here is the code attempt, which I would like to get running
Keyboard.printf(KEY_CTRL);

Start from the reported Keyboard.printf(KEY_CTRL) call and trace how the library handles modifier keys versus printable letters. Reproduce the attempt on the ArduinoCore-mbed library and determine whether completion means sending a pressed modifier rather than outputting its key name.

Written by the indexing model from the issue text.