In the tenth century AD, merchants simplified the Sharada script for quick note-taking. There were a number of common features in their scripts, common enough that the name “Landa” was given to all of these scripts. However, as Landa was used mostly for quick, mercantile notes, there wasn’t a significant reason to standardize, and so regional variations appeared. The variations could be classified into two major groupings, one used in Sindh (called Khudawadi) and one in Punjab (called Multani).
One way that the merchants simplified the script was to omit the vowel-changing diacritics. (Remember, as an abugida, Khudawadi has an inherent vowel, which is changed by adding a diacritic.) In some sense then, the simplified merchant script was more like an abjad than like an abugida.
In 1860 AD, Khudawadi was regularized and formalized for official use in Sindh, and as part of that, vowel diacritics were added back to Khudawadi. There are also more characters in Khudawadi than Multani due to there being more phonemes in the Sindhi language than in the Punjabi language. There are also differences in the glyph shapes and minor differences in the sort order.