[HGuderian]

Try this way:
a) make a copy of Mbug_Slovakia_winter's load.ini
b) then rename it (for example) MbugW_load.ini
c) put it into Slovakia map's folder
d) add to all.ini (into MODS/Maps/mapmods folder) a new entrie such as "SlovakiaWinter Slovakia/MbugW_load.ini" (w/o "")
e) add to config Custom(number you choose)=SlovakiaWinter
f) make consequential corrections to your .mis files, so MAP Slovakia/MbugW_load.ini
g) name .mis file SlovakiaWinterBlue00None
h) fly in QMB your new SlovakiaWinter map

I hope this work for you