This character is a Other Letter and is mainly used in the Arabic script.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it is written as Arabic letter from right to left. When changing direction it is not mirrored. The word that U+06A6 forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with 4 other glyphs.
The Wikipedia has the following information about this codepoint:
Sindhi (; Sindhi: سِنڌِي(Perso-Arabic), सिन्धी(Devanagari)[sɪndʱiː]) is an Indo-Aryan language spoken by about 30 million people in the Pakistani province of Sindh, where it has official status. It is also spoken by a further 1.7 million people in India, where it is a scheduled language, without any state-level official status. The main writing system is the Perso-Arabic script, which accounts for the majority of the Sindhi literature and is the only one currently used in Pakistan. In India, both the Perso-Arabic script and Devanagari are used.
Sindhi is first attested in historical records within the Nātyaśāstra, a text thought to have been composed between 200 B.C. and 200 A.D. The earliest written evidence of Sindhi as a language can be found in a translation of the Qur’an into Sindhi dating back to 883 A.D. Sindhi was one of the first Indo-Aryan languages to encounter influence from Persian and Arabic following the Umayyad conquest in 712 CE. A substantial body of Sindhi literature developed during the Medieval period, the most famous of which is the religious and mystic poetry of Shah Abdul Latif Bhittai from the 18th century. Modern Sindhi was promoted under British rule beginning in 1843, which led to the current status of the language in independent Pakistan after 1947.