I created Slovenian layout file, for keyboard library. If anyone from Arduino wants to add it in official Arduino library let me know. I can send you KeyboardLayout_sl_SI.cpp. Or anyone else from this forum.
Layout is tested, so everything should work.
To load Slovenian layout: Keyboard.begin(KeyboardLayout_sl_SI);
Tested with next string:
"!"#$%&'()*+,-./0123456789:;<=ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^`_abcdefghijklmnopqrstuvwxyz{|}~ @"
Due to how the Slovenian keyboard works, some characters (~, ^, `, etc.) have to be pressed twice. There are two ways to do it.
Example for ~:
#1: AltGr + 1 + 1
#2: AltGr + 1 + SPACE
This means that the required test string can also be done in two ways.
#1 "!"#$%&'()+,-./0123456789:;<=>?ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^^``_abcdefghijklmnopqrstuvwxyz{|}~~ @"
#2 "!"#$%&'()+,-./0123456789:;<=>?ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^ ` _abcdefghijklmnopqrstuvwxyz{|}~ @"
I would attach a file, but i don't see any options for attachments.
Edit: Slovenian keyboard layout is Qwertz not Qwerty. Just in case that is important or needed info.