What is the ruling on repeating the Tashahhud in prayer due to absentmindedness, in order to attain full devotion?

The fundamental principle regarding the remembrances (adhkar) in prayer is that they should not be repeated, except for those explicitly mentioned in the texts to be repeated, such as the glorification (tasbih) in bowing (ruku') and prostration (sujud). The Tashahhud is one of the remembrances of prayer, and its repetition is not legislated. If a worshipper doubts a pillar (rukn) or a واجب (wajib - obligatory act) while in prayer, they should perform it. However, repeating what the worshipper has already said due to absentmindedness is not legislated, as it opens the door to obsessive whispering (waswas). Therefore, one should strive to attain devotion (khushu') as much as possible, and there is no need to repeat prayers that have already been performed.