Is it permissible to leave a job at a company that sells cosmetic products (dark dye and for women who display their adornments) despite the employer taking a blank promissory note, knowing that he forbade prayer in the mosque and commanded group prayer in the office?

If it is highly probable that the company's products are used in unlawful activities, then it is not permissible to work there, as it involves assisting in sin. Obedience to Allah takes precedence over obedience to creation. Preventing congregational prayer in a nearby mosque is not within the right of the employer. As for the receipt, if you signed a blank paper and fear that a large sum might be written on it, then you have erred by exposing yourself to danger. However, if you possess the paper, you can write the amount actually demanded. If nothing is demanded from you, you can destroy it.