Question how to expand timing of sub/idx subtitle

[jimdagys]

I know that I can use Subtitle Workshop to expand (lengthen subtitle duration) of srt subtitles (see screenshot). However, I want to expand (not delay) sub/idx subtitles, and Subtitle Workshop won't allow me to input sub/idx.
Subtitle Creator only allows me to delay sub/idx subtitles.
My question is: What software can be used to expand sub/idx subtitle timing?

[jimdagys]

Does anyone have any ideas on the above question?
I tried Easy Subtitles Synchronizer
but that doesn't seem to work with sub/idx subtitles.