Is it possible to create something like the following with a single tempo mark but including confirmation of the details (including the combination of plain and boldface text)?
Ex: Tempo I (Andante comodo (♩= 92))
You can’t easily nest parentheses like this in a standard tempo item, no. So I suggest you create the required tempo and hide it by setting both its text and its metronome mark to be hidden via Properties, then create a system-attached text item that looks as you want it to appear (shortcut Shift+Alt+X).
Thanks, Daniel. I suspected that was the case.