How do I create two eights = 140 as a tempo marking?

How do I create this tempo marking? Stravinsky Rite of Spring

MusGlyphs font is your best bet there.

This is quite spectacular indeed. Too bad I cannot use this font in the (Shift+T) tempo box.

The tempo box is semantic, and therefore it’s going to be limited in what it can parse.

You can set tempo and hide it, then type as system text, bold.