A .srt file is a simple text file, containing just the data, without any formatting. You’d need to change the font size in VLC Player. Is this what you tried?

https://wiki.videolan.org/VLC_HowTo/Adjust_subtitle_font_settings

Thanks for your info. OK, I was surprised to see the .srt file is just the subtitle text for every second of the video. And I guess the settings for the position of every text part in the dashcam app ist only for displaying within the app.

I have the free version “3.0.12 Vetinari” of the VLC player, and yes, I was in the preferences for subtitle/OSD. But there is no “Text renderer”, instead there are — oh, just now I see there is a “simple” and an “all settings” mode, so the text renderer is available to choose.
OK, I will experiment with these settings, and find out what the different renderer “modules” mean.
Thanks again!