Could you add an option to keep the video playing while the settings window is opened, this is specifically to adjust the subtitle precisely instead of keep going back to the player to check, and may be add keyboard shortcuts for subs delay instead of having to open the settings window.
I don’t know if you are using catalyst to build Mac version just out of iOS version.
My suggestion is to please make a native app, because I am kind of a half iOS developer and I know that there are a lot of bad experiences when using a catalyst app. (For example, for now the movie will stop if I want to change some settings like subtitles.)
And stability of catalyst app will be reduced somehow.
I don’t know if this will increase your workload, but anyway thanks for making the Mac version.