How to ovrd center-align to left if lines starts with dash?

[Aray]

https://res.cloudinary.com/aray/image/upload/v1567199548/Screenshots/Ovrd_Center-Align_to_Left_if_Starts_with_Dash.jpg

As shown in the figure, the top one is Actual behavior, the bottom one is Expected behavior.

Is there any possibility that two lines begin with dash on SRT or ASS subtitles, it'll be automatically center-aligned to left Just like on Blu-Ray Subtitles?

[sneaker_ger]

I don't think ASS has a function for that. The simplest way would be to create a 2nd ASS style for those lines (Aegisub offers regex for line selection) and put them into a second style that is bottom-left aligned with a big MarginL (or \pos tags) so that the subtitles are actually in the middle. The problem is that subtitle lines with different lengths would need different MarginLs to be exactly in the middle so in the end it might need a lot of manual corrections to get this done perfectly.

Maybe there is some way to get this perfectly automated in Aegisub but I don't really have a clue about that.
http://docs.aegisub.org/3.2/Automation/