I just added the dark theme when using the expanded version (it was an omission on my part). It will be there in the next release.
For the line & character indicator, do you mean when you are looking at GTM Preview and there's an error in your tag?
There's already a Da Vinci Tools feature for Data Studio which allows you to refresh at different intervals, but not on a per-item basis. That is, all the underlying data is being refreshed. Or do you mean something else?
I'm unable to reproduce the problem, but it might be because the heatmap button is on top of the sort button area, so clicking just a little bit beside it will trigger the sort.
Fixed for next release. I also noticed the icon wasn't showing up correctly, so I fixed that too.
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