I am trying to use custom themes to alter the appearance of straight tables.
From help.qlik.com (Widgets & Extensions \ Custom themes):
CSS styling is more general and flexible.
However, none of the following articles describe how to use css. From the "extended object styling" article, I gather that one may change (only) the header font color and size, and the content font color and size, using JSON.
Are there other things I can change through css? What I currently need in particular is the thickness/color of the header base line. However, in a "teach a man to fish..." fashion, I'd like to know if there is a place (in the code?) I can check to discover possible customization options.
Try inspecting the HTML with the browsers developer tools. They also allow you to try your changes, add css style definition by hand etc. Once you are satisfied, put your new CSS rules in a stylesheet.
Erik Wetterberg https://extendingqlik.upper88.com/