FontBase supports variable fonts. You can access this feature in two ways:
- Open the respective font's Family page (double-click a font in the list or click "View family"), then navigate to the Waterfall tab. You will see the font property sliders (for variable fonts only) to adjust.
- Navigate to the Preview page using the controlbar on the left, select a text box, then find a variable font in the font selector dropdown within the STYLES section. If the font you've selected is indeed variable, you will see a VARIABLE FONT section with respective font property sliders.