If you're talking about uitable within a uifigure, then it does not support html formatting. See https://www.mathworks.com/matlabcentral/answers/470734-matlab-uitable-column-font-size-using-html-not-working
If you're talking about uitable within a figure (old style java-based), then you can use html formatting although this is undocumented.
As for R2019b, one condition of downloading the pre-release is that you can't talk about it. Once downloaded you can look at the release notes to see what improvements have been made. There are several with App Designer.
