The Dawoodi Bohra community believes Laylat al-Qadr was the 23rd night of Ramadan. Dawoodi Bohras are a Shia Muslim community within the Tayyibi Ismaili tradition, with strong historical roots in Gujarat and a worldwide community today.
Laylat al-Qadr, or the Night of Power, commemorates the night associated with the revelation of the Quran and is described in Surah al-Qadr as better than a thousand months. The Quran does not specify a calendar date, and many Muslims seek it during the final ten nights of Ramadan.
Sunni Muslims commonly emphasize the odd-numbered nights—21, 23, 25, 27, and 29—while many Shia traditions give particular importance to the 19th, 21st, and 23rd nights. The 23rd-night observance is therefore not exclusive to Bohras, but Dawoodi Bohra is the specific Ismaili community identified in this question. Nizari Ismailis, Alevis, and Alawites are distinct communities.