The text caption of the button is simply a string.
So whatever you like really? The code to get the button text/caption is likely to be the same regardless I would imagine. Then you just need something (a flag, global variable or something?) to indicate the language in use. A DB might well be easiest as you head up the columns as language names. So you could easily have the primary key/column being the button name then store all possible language values for each.
Database: https://support.smartbear.com/viewarticle/75176/
Equally, a CSV or Excel file would work just as well.
Excel: https://support.smartbear.com/viewarticle/74555/
I don't do multi-region support. but I do read in data from various external sources. Mainly XLSX, TXT, CSV and SQL files. As well as reading from external SQL DB's. It's straightforward enough really.
