From a list of public git repos, a job (a small program that runs regularly) fetches every tag, verifies library files and push the updated list onto the Arduino download server. Only valid libraries and their tags are published. A library is not valid when:
The job runs every hour. If a new library has been released, you can expect it to be listed within the hour.
Just tag your library once more and push the new tag, or create a new release with github "releases". Our job will eventually fetch and publish your new release.
Open your sketchbook "libraries" folder with your OS file explorer (win: explorer, mac: finder, linux: nautilus, kfiles...) and delete the folder containing your library.
No, we don't have a delete button. Libraries managed by the Library Manager are mixed with those you've manually installed, maybe libraries you've written: making a mistake and deleting the wrong library is too easy. That's why trash bins exist. Since the IDE has no knowledge of your trash bin, we didn't implement a "delete" button.
At the moment, the IDE handles one URL only, and that's written into the code (dev jargon: it's hardcoded). This is a known limitation. However, if you know your way through the code, you can change that URL with another one.
No, at the moment library dependencies are ignored. Current Library Manager aims at simplifying your life when dealing with installing a single library. If a library depends on another one, you'll have to install both.
Library Manager installs libraries into your sketchbook "libraries" folder. Since you cannot create two folders with the same name, we can't install two versions of the same library. However, you can switch between library versions, by selecting the appropriate one from the version dropdown that pops up on Library Manager when more than one version is available.