You simply need to right-click on the panel > add new to create a new entry setting a name, an icon and a link. Useful ones are:
The same links can be used also in the folder view plasmoid, in the image below for example the links are:
activities:/current (available also as option in folder view path)
Here you can see the link “settings:/” in action:
And finally in the image below there is a compilation: I added the link “tags:/Android” to show files I tagged with “Android”:
(for curious: the Downloading and Seeding folders are the places KTorrent automatically put downloading and completed torrents)
Now imagine to combine this tool with Activities: you can see the files linked to each activity in Dolphin, the same for tagged files, add different folder-view plasmoids on each activities using tags, activities-linked, chronological links, in addition to “normal” folders. Folder-view plasmoid also let you filter files by type and name-scheme. If you spend some minutes in setting your workspace and acquiring good practices, you will gain a superior desktop experience.
Since I care about details, let me say I really appreciate the fact I can set different icons and names to resources entries without changing the original folders and I can set custom names to folder-view plasmoids.