Is it permissible to set aside ten minutes before each prayer for preparation, ablution, reading the Qur’an, or engaging in dhikr, while observing silence or repeating the adhan during its call, in order to attain khushu' in prayer?

May Allah reward your eagerness for good and your desire for it. Preparing for prayer with remembrance (dhikr) and emptying the heart for it are among the best aids to achieving devotion (khushu') in it. Awaiting the next prayer after a prayer is considered Ribat (guarding the frontiers) in the path of Allah. This means the heart remains attached to the prayer after performing it, whether by sitting in the mosque or by the heart being connected to it while engaged in work. Congregational prayer in mosques is among the best deeds, and one should be keen on performing it. Following the muezzin and repeating what he says is a recommended Sunnah practice.