I would like to be able to split lines longer than 100 characters into multiple lines less than 100 characters long in IntelliJ IdeaVim. The Vim solution in the vim command to restructure / force text up to 80 columns does not work.
It is not yet implemented in IdeaVim. You can vote for https://youtrack.jetbrains.com/issue/VIM-1310 around :set textwidth and https://youtrack.jetbrains.com/issue/VIM-186 about :set textwidth comments.
:set textwidth