There are several ways to update all of the fonts used in your Altia GUI. 2 methods offer font switching at runtime (altiaSetFont and altiaBulkSwapFont). Please refer to the User's Guide for details on these 2 methods, as there are some pros and cons, and they are not supported on all DeepScreen targets.
If you would like to swap out all fonts (or just a lot of them) at design time while using Altia Design, you can do a search that returns all defined fonts - even on parent containers (this works in 11.x or newer). Note the parent Group (2) in the screenshot below:
Use the Find’s search criteria in the screenshot above (the middle “Find Font” tab is the key). The default search string “.*” will return every font definition on any object in the model. You can then use the Navigator pane's "Advanced Attributes" to change the font(s). TIP: Make sure to click the checkbox in the top-right of the Navigator pane to filter the Navigator pane to only show the Find pane results. In the filtered Navigator view, you can range-select many Text I/Os at once (perhaps a range of all Text I/Os with the same font/size) and change all of those fonts at the same time.
NOTE: This is the best solution for changing fonts at edit time in 11.x/12.x. However, there is an even easier method designed just for this coming out in a new version of Altia Design, but that is not yet available yet at the time of this article's creation.