Where font files are supposed to inserted? in input section or in attachment section?

i am mixing multiple files like - subtitles, video , audio and fonts into one. i am new to this so i dont know much, like in pic below there are 4 font files out of which two are accepted into input section whole other two dont.
on the other hand all 4 font files are accpeted in attachment section

why i am asking? bcz i have two subtitles but after mixing i see only one in vlc player , so i dont know what i am doing wrong

Fonts (in your screenshot: the first & last three TrueTypo/OpenType files) all need to be attachments; the other files (AVC, FLAC, AC-3, ASS) are all source files.

In general you can assume that:

  1. all file types that contain content that changes over time or where content is associated with timestamps are source files; they need to be used on the “input” tab
  2. all other file types are attachments

If you try to use font files (which do not have content associated with timestamps, obviously) as source files & they’re accepted, then MKVToolNix mis-detected what they are. This can happen from time to time as a lot of media file types are difficult to auto-detect with absolute certainty.

thanks you so much for explaination