I'm playing around with this a bit. (I'm actually doing it in 2019 beta, but that feature is the same there (I think).)
If I set a sheet's color to none, the sheet (but not its marks) becomes transparent. If I have row banding turned on and if I turn off the sheet's colors, the banded rows keep their colors and the other rows are transparent. I have to set this in the FORMAT function for the sheet. I don't have access to opacity where I set a color for a sheet, so it's all or nothing (transparent or opaque.)
For a filter, I can set the color in the FORMAT function, and there I can also mess with the opacity. So I can make it semi-transparent. Pretty cool.
For either object, I could enclose it in a container, make the object itself transparent, and mess with semi-transparency by coloring the container and sliding the opacity up or down.
At TC18 the Devs on Stage showed another feature where a container of filters was set to transparent and the whole thing disappeared and a little eyeball-shaped icon took its place. Click the eyeball and the container came back. (Or at least that's what it looked like.)
I guess that's a feature yet-to-be-released. Any idea on the ETA for that?
The feature that hides/shows a floating layout container is coming early next year. It's still under development by my team.
For now, the viz (background) transparency feature is all or nothing. We may add alpha channel control in a future release. As you've pointed out, you can use the dashboard Layout tab's Background color to change the viz's dashboard 'zone' color. This color has a slider for opacity control.
You folks are doing cool stuff Phil!
Cheers for sharing this Phil, a lot of excitement about these new features
[Program Manager - Tableau Community]