Is it permissible for an employee who works as a custodian of a financial trust in a company to profit from it while preserving it and without the permission of the company owner?

It is not permissible for you to use the company's funds entrusted to you without the owner's permission, because a trustee is not allowed to dispose of what is under his hand except according to the owner's condition. Violating this condition is forbidden, as the Prophet (peace and blessings be upon him) said: "Muslims are bound by their conditions, as long as they conform to the truth."