go to the profile folder, there you'll find the autoexec.cfg (or autoexec_a2.cfg) file. Add the following line to the end: setvar dev_console_password = schwinge-des-todes
Next, in the Documents/My Games/HoMM5 folder, find your profile in the profiles folder. There you'll find the input.cfg (or input_a2.cfg) file. Find the console section and add the following line to the end: bind show_console '`'. There is also a file in the game folder, but it doesn't work.