I upgraded by OS and the GImp as well with it.
So the gimp now has the tool box all different.
Typicall to these kinds of things, changes are often arbitrary.
the toolbox was arbitrarily changed to default to 'use groups' so you will not see all the options in it till you go to preferences and uncheck the 'use groups'.
Sometimes it seems as though it's just a powertrip by arbitrary software tyrants. And if you read the comments on line the respoinses are often 'well you should know that you need to read the release notes'.
So anyway, my point, when you get this new gimp, it will be set up in a way that is purposefully made to make it harder to use unless you are an insider and know all the changes that they arbitrarily made.