Save caption style / create preset
That would depend on what software you're using - would you be able to clarify?

In Premiere Pro you can use Essential Graphics to drive your captions (there is a number of captions presets in the EG panel already, just go to Essential Graphics\Captions and Subtitles and select the one that best suits your video) - the editor has plenty of useful options and you can save your styles as 'Masters' and reuse that style for each subsequent video. Alternatively, you can create your own Essential Graphics template for captions via After Effects to have full control over them.

More info on Adobe's help site.