nd then user can only guess whether the change of settings was accepted or failed.
If it can't open the port then it can't change the settings, so I don't see how any guess work is involved.
s soon as you will click OK in this window Tera Term will try to open serial connection on currently selected serial port. The error message may pop up if selected port is in use by another application. This error message should be ignored.
If the port is open in another application/instance it BETTER pop up a message saying it's in use. The message seems quite correct to me.
As far as your other post goes, if you set it to open a serial port connect by default and you open another instance, again the message seems correct. It's already open, so what else would it say? If you want to open another connection type then 'File | New Connection...' works to do that.
Not trying to be argumentative, but it's been this way since as long as I can remember.