Is it permissible for a government employee who works as a legal researcher, and for whom there is currently no specialized scribe available, to write procedures for clients for a fee, especially since there are scribes outside the office who exploit clients? And is it permissible to accept gifts from clients on special occasions?

What you are permitted to do during official working hours by the responsible authority incurs no sin upon you. Otherwise, it is not permissible, because the employee's benefits during his working hours are owned by his employer. So, if the employer permits him to utilize these benefits, there is no sin upon him. The employee is a private hire whose benefits belong exclusively to his employer. Similarly, client gifts require the employer's permission, and customary permission is equivalent to explicit permission.