show taxonomy list in columns

That’s certainly possible. The specifics will depend somewhat on how your theme displays widgets (many themes already split widget areas into different columns). However, you can style this widget to display in multiple columns using CSS:

.list-custom-taxonomy-widget {
    column-count: 2;
}

.list-custom-taxonomy-widget .widget-title {
    column-span: all;
}

You can add CSS like this by copying the excerpt above and pasting it into the “Additional CSS” option in the customizer. Note that Firefox won’t support multiple columns this way until the next version is released; do some research on browser prefixing in CSS for more information. This excerpt will apply to all list custom taxonomy widgets; you can target specific ones with more specific CSS selectors.

• This reply was modified 7 years, 9 months ago by Nick Halsey.