Boxes (bold upper rectangles) with A, B, C. above the staff

Hi all,

If you look at my attached score, you will see (at mesures #35, #51, #63 and #79) boxes above the staff with a capital and bold letter in each of them. They are used to identify repeating parts in a piece and the boldness of the lines/font makes it easier to locate.

How can I produce these with MuseScore 3,5? I searched but could not find how.

Thanks in advance,

Alain