While trying to learn SketchUp, I created a lot of Groups I don’t need. I read the Help for deleting Groups but that referred to the Pro version. The Web version (2021) I’m using seems to have a different UI in this regard. While wandering around, I discovered that selecting a Group in the Organizer and pressing the Delete key seems to remove the Group. Multi-select also seems to work!
Am I missing anything?
The Web version and Pro do indeed have a different UI although although most of the functions are the same. Groups and Components are deletable directly as entities by selecting them and pressing delete, or multiselecting and pressing delete or through the Outliner as you discovered. When you do this all geometry contained in the group is removed. If you just want to “un-group” the geometry but keep it in your model you would right click and choose explode. Components deleted this way will be be deleted from your model but are still available in the component browser to insert again, unless you purge the model, groups are gone forever (still kept in the undo stack).
I don’t think you are missing anything.
To expand a bit on EF’s remarks, deleting groups, whether needed or unneeded is as simple as erasing them with the eraser tool or right clicking on them and choosing Erase or hitting the Delete key. There’s no such thing as “unused groups” at least in the way there can be unused components or unused materials. Delete a group from the model space and it’s gone.
Components, on the other hand, are still held in the model file even if you have deleted all instances of them from the model space. This can bloat your file if you have a bunch of unneeded components so purging the unused is a good idea. That’s done by clicking on the Recycle button at the bottom of the Components panel.
This can also be a good back up. If you Hide using the Context menu but accidentally hit Erase, the on screen appearance is the same but when you go to unhide later, a group will be gone entirely while a fresh instance of the component can be dragged in from the In Model components (as long as you haven’t purged) and potentially save you a lot of work.
I sometimes leverage this feature of components by modeling a component in a convenient location in the model space, then deleting it and bringing in a fresh copy from the In Model components. It’s sometimes easier to precisely place a component that way than it is to move it around the model space to place it.