Consider using subtitle regions for this. While the term "
region" originally referred to the screen/display area to show the caption in, it can include font/size/other formatting properties ("style") now.
As an example approach, I can:
• add a subtitle track, right click on the new subtitle track and add two subtitle regions.
• rename each region to reflect area (e.g bottom-left, bottom, bottom-right).
• select a region, and in the inspector, customize the track settings as appropriate. This is easier to preview when I have captions on that region and the playhead is on top of a caption.
Now any caption I add/move to that region will take on the settings for that region. One approach I might consider taking is to customise the position and font size for a region and override (say) font family or color on individual captions to reflect the character speaking the words. this way, when a character moves across the screen, I can move the caption to the appropriate region and retain the font/color overrides.