Why Doesn't MKVToolNix GUI Save Chosen Properties?

I use MKVToolNix a lot. I’m on macOS and I use both the homebrew CLI stuff for mkvextract and other stuff, but mainly I use the macOS GUI app for basic editing and multiplexing.
Problem/Question: When I’m editing an MKV file, usually one I’ve downloaded and which has inadequate properties identified, I fill out the properties that are most important to me.
But when it comes to SUBTITLES, there’s a problem. In the Multiplexing tab, I choose “Default=Yes” and Track Enabled=“Yes” as well as “Original Language=Yes.” I also name the subtitle, like “SRT” or similar. Then I save my changes.
However, when I reload the file I just worked on and look at the INFO tab in the GUI, the only values I entered in the Properties panel that were saved were the title and original language. The “Default Track” and “Track Enabled” values that I set to “Yes” still show up as “No.”
Can anyone tell me why this is?
For the longest time, I’ve wondered why, when I bring my saved .mkv files into Handbrake to re-encode, I always have to set the default value on the subtitle again.

Please read this FAQ entry. It addresses what you’re observing and why this is not a bug but just how Matroska works.

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thank you kindly for your reply & helpful info.