It is currently not possible to add a skill to the end of the queue via click and drag. It can only be added to the second last slot. In the existing skill queue you can do that.
You can also not add a skill to the skill catalogue by dragging it onto the skill list. Adding that would be an improvement over the existing Right Click → Inject or dragging to the skill queue.
Another improvement to reduce clicks would be this:
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Don’t worry. The market window and all other windows will eventually get the same treatment and you will have to enjoy huge windows with tons of empty space and not customizable UI parts because CCP knows best what users want. I prefer the market window design over the new design, to be quite honest. You just need to look at how much information it packs into a clear, crisp and economical interface. Now compare that to the bloated, wasteful and information-hiding UI of the new skill window.