LR will not scroll like you describe Picasa doing it.
If you have the Folder panel displaying all the folders with the correct parents (right-click, show-parent), you can turn on the option to "show images in subfolders", then click on one of the parents and see everything under that folder.
There is also the "all pictures" collection at the top of the left pane.
I don't see "show parent" on a right click on any subfolders, my assumption is this as it pertains to parent Pictures>2015>folders>photos. But I did try the "all pictures" and that appears to do what I asked. Thanks
"Show Parent Folder" will appear when you right-click on a folder, if the parent is not shown. If the parent is already shown, then "Show Parent Folder" will not appear.
To make a minor technical correction for anyone else who is reading along, you want to look for "All Photographs" and not "all pictures".