I've tried two space-saving arrangements for hotbars.
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I should say I was warned this first approach was utterly insane, so.. if it doesn't make sense to anyone I shan't be surprised or offended. If it's of no use to anyone, feel free to disregard it.
The top left picture shows a 6x6 array of horizontal hotbars, further illustrated by the arrows. Hidden underneath that, as we see by the handles poking up, is a 6x6 array of vertical hotbars.
If we click on all the vertical hotbar handles across the top, it brings all the vertical hotbars to the fore, as seen in the top middle picture. This presents us with another 36 cells, as distinguished by the downward arrows, without taking up twice as much screen space.
Clicking on any single hotbar handle will bring that row or column to the fore. It could result in all sorts of patterns of cells, as represented by the scattered arrows in the top right picture. You would have to carefully plan which cells held what information, or at least be flexible about how you accessed them, for this to work.
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Perhaps a slightly more efficient arrangement in terms of organisation, less so in terms of space, would be the lower left picture.
Here we have a 5x6 array of cells made from horizontal bars, represented by the arrows pointing right. Below that we have another array of horizontal hotbars, 6x6. The rightmost cell of each of these hotbars can be seen from underneath the uppermost hotbars, represented by the left-facing arrows.
Clicking on all these rightmost cells brings those bars to the fore, as per the lower middle picture. In this example the hotbars are locked so that the handle doesn't overlap the top one. You could just stagger it half a cell but I liked the neatness of the cells lining up. You could also make the bars shorter on the left end.
In this arrangement, one horizontal bar basically overrides another, so you would put mutually exclusive things in the alternate hotbars, or at least stuff you didn't need to access simultaneously.
Depending on the application, you may or may not want clickable items in those rightmost cells. Something that might work as a clickable would be a tool like a sewing kit. When the underbar comes to the fore, it could have information or items pertinent to tailoring, such as leathers, bone, cloth, arcane gems, and so on. That way when you click to sew something, all of your related inventory is displayed.
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Myself, I haven't really thought of stuff for it yet but I'm considering using these layouts as I'm running low on space. Scaling the interface isn't really an option as it seems to carry over onto characters that have no such issue, plus it makes things harder to read or click.
I might put all my RP emotes and related stuff in one array, then overlay it with another that contains stuff that I gather while hunting. That way I can have a town/dungeon toggle to my hotbars.
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If anyone knows a Command script that can bring several hotbars to the fore at once without the need for clicking, it might save me some tricky arrangements.
