Hi @rrodriguez,
in this case of update (no upgrade path to new version) it is required to install extensions again. See here how to retrieve list of extensions you have installed: Knime Extentions list - Did i miss something?
When starting KNIME 4.2.0 for the first time you’ll be asked about workspace location. Point it to your old location and your preferences/settings should be same.
(It is always recommended to have a backup of your workspace.)
Br,
Ivan