Is it permissible to return to working in a conventional bank after leaving it due to the bank's expansion in employing women without restrictions, knowing that the bank has not completed its Islamization plan, and that the current job is in a bad environment and has financial burdens?

Your departure from the bank to expand the employment of women without restrictions is a sign of good, for whoever leaves something for Allah, Allah will compensate him with something better. It is not permissible for you to work in the bank if its Islamization is not complete, or if there is mixing between men and women. If it is possible to work in the bank away from usury and mixing, there is no harm in returning; otherwise, be patient and seek reward from Allah.