Adding new tied note to chord replacing second chord in tie with single note.

Hi there,
Relatively new musescore user. In the documentation for MuseScore 3 it states that when adding a tie to a new note in a chord in Note Input Mode:

"Note: This shortcut works, as described above, only if there is no chord following the selected note. If there is, then the duration is ignored and the tied note is added instead to the following chord."

However, when I add a note to an existing tied chord and then add the tie to that note using plus sign, the second part of the chord disappears and is replaced by the note. See the following screencaps:

What am I missing? Any advice?
Thanks,
Neil