It is done with 2 keys, one for increase, one for decrease.
Its working also in interiors, like caves, where you don't have a map. This is of great help while exploring big caves.
Installation
1) extract the files in your Mods directory; if it doesn't exist, create it in the game directory.
2) add 2 lines in your file input.settings :
IK_NumPlus=(Action=MinimapZoomPlus)
IK_NumMinus=(Action=MinimapZoomMinus)
In my case, I use 2 keys in the numpad (+) and (-)
You can use others keys, if you want.
You have to place these 2 lines in the following tabs
+ Boat
+ BoatPassenger
+ Diving
+ Exploration
+ Exploration_Replacer_Ciri
+ Horse
+ Horse_Replacer_Ciri
+ Swimming
File Locations
mods : in your game directory : X:\The Witcher 3 Wild Hunt\Mods
input settings : C:\Users\username\Documents\The Witcher 3
Problems
If one of your mods use the file
...\The Witcher 3 Wild Hunt\Mods\modMinimapZoom\content\scripts\game\player\playerInput.ws
There will be a conflict. So you have to merge the files.
Changelog
1.1 : patch 1.10
1.1.1 : corrections
1.2 : patch 1.11
1.3 : patch 1.12