i am working as a software quality analyst in a startup, i have to perform manual testing on multiple websites in same time, so manager do not force me to write any documentation like test cases or test scenarios, they just want a bug report in which bugs are properly elaborated and i am doing this efficiently, but confusion in my mind is, working without any documentation like test cases etc would affect me hard when i will join any big company/corporate because there they require proper documentation included in QA field?

writing test cases for all project is a good approach but seems impossible for me, cause i am only Quality assurance engineer in this startup.