I’ve got 4 social media icons in my back matter. They’re side-by-side on the same line and compiled just fine in Scrivener 1.
I just got Scriv3.
Now they compile vertically in a column, each on its own line. So I moved them into a table. But the table remains left-aligned and will not centre.
What am I missing?
Gathering you’re Compiling to e-book or HTML, either use text-align: center; or margin: 0 auto 0 auto; in the stylesheet for that table.
In Scrivener, this usually happens when you press the Align Center button in the Editor.
If not, give it a Paragraph Style and amend the stylesheet in the Compile Format Designer’s Css-tab.
Thanks. I should have clarified that I’m compiling to ebook.
Big changes from Scriv1. I was actually using “No style” for everything. And the dropdown (which I didn’t notice before) on the compile screen was set to “Text and notes use default paragraph formatting” (rather than custom or wysiwyg in editor).
I’m using the default Centered Text style and that seems to work, but only if the images are in a table. But then even with border:0px, the border still shows up in the ebook.
Deep in e-book creation using Scrivener, I can advise you to keep Calibre close by and open test results compiling one document at a time. In the CSS-tab in the Compile Format Desginer we can see what elements gets the border: 0px; attribute. It might not be the table. 
Check the html and the stylesheet in Calibre to find out and adjust Scrivener. Using Paragraph styles in the Editor you might get a handle on the html-container element to style it to your wishes. 
hth, if you have more questions, let me know.
Thanks again. I do indeed keep Calibre at hand (usually always open on my pc). Although I’ve noticed that its ebook reader doesn’t do justified text too well. (Either do a couple other Window ebook readers I use.)