Ubuntu – Can Shotwell create a folder structure based on the date the photos were taken

Not yet. Shotwell can organize your photos into folders by time only, like the first link you have. To achieve what you want you need to use the Hierarchical Tags feature in Shotwell. This isn't exactly what you want though, so the short answer is no.

Have a look in Preferences/Library/Importing/Pattern: and click (Help) for a list of exactly the time-based metadata Shotwell can organize by.

If you are just wanting to separate out groups of photos to export, you can select a group of tagged photos and export them to a new folder. From there, you could manually reorganize your Pictures directory structure in the file browser.

The simplest way to achieve this is with tags, not events. The short answer is to manually import folder-by-folder, and tag each batch of imports.

The first decision you have to make is whether to preserve your directory structure, and keep pictures in folders like you have them now. Shotwell defaults to a date directory structure, you have an event structure.

If you don't care, have all the photos outside /Pictures, and import one folder at a time using File/Import from folder... . Tag each batch as you go. All your photos will be reorganized in /Pictures based on dates.

If you want to keep the event structure, make sure to un-check the 'Watch library directory for new files' in Edit/Preferences/Library. Move all the folders with photos into /Pictures. Then import one at at a time, again tagging each batch of imports as you go. You will have to keep maintaining the library from then on, manually importing photos.