How to change horizontal category on a data series or manually create a legend

Hi,
So I had trouble formulating a title for my problem, but perhaps it is easier to explain with a picture of my graph.

Namnlös.png

This is how it currently looks, but I want the green bar to be in experiment 2 and not in experiment 1 while still having 3 legends.

Namnlös 1.png

This is how I want it to look, but of course more professional-looking. I would prefer it without the weird invisible bar in experiment 1. By "cheating" this way the spacing between the bars is also off.

I currently have three data series and two "horizontal categories". One of the data series are composed of two values, which I want to be under both categories. The other two data series are only composed of a single value, and I want one of them to be under the first horizontal category and the other under the second. I've thought about trying to manually change the horizontal category it is in, but to no avail. If I could manually create just a legend with no data in it that would also solve it. I don't know if it is possible to do either of those though.

I hope my explanation of my problem is understandable enough, any and all help is appreciated!

Warm regards,
Lymoz