Wenyan-lang does this, but it's not really common in normal texts. The reader is just expected to figure it out themselves.

Also note that màn dé bó is the Pinyin transcription of 曼德博 and only reflects the Mandarin pronunciation. In Zhengzhang Shangfang's reconstructed Old Chinese pronunciation, it would be more like moːn tɯːɡ paːɡ. Those syllable-final consonants are preserved in many other Sinitic languages, like Cantonese (that's how they were reconstructed) so Mandarin-based transliterations don't work well for those. As an alternative, 勃 (also Mandarin bó) has the reconstructed Old Chinese pronunciation bɯːd, which is a closer approximation of the "brot" in "mandelbrot".