After some time looking to get back the behavior of the MaxScript help previous to 2012, I couldn't find any information to do:
Press F1 to open the CHM Help file (not a combination of keys)
Open a single instance of the CHM file
Pass the selected word to the Index tab.
Finally with the help of a "lost" little utility, I got it working (mostly) as it used to be.
What do you need?
1. The CHM file
2. The little utility "KeyHH.exe"
You can download the CHM files from the following links:
3ds Max 2012