Looking at the 3.png, I believe your editor toolbar is already working.
I think it is a bug. I went to my package manager, I just found that it was not installed but I've already been using it since a year ago if I remember correctly. I tried to uninstall or install the package, it still here (can't be removed).
Editor toolbar is very useful. I put my frequent-used items there, no more looking for items on the main menu. I use Lazarus 1.6.4, I never had "Unable to load package" message.