In addition to the answers, it would seem important to me that you find out IF you are actually letting bugs slip through. The way you write this would make it seem the software is up and running in production, so surely if there are bugs they would be reported. Then you can check if you should have been able to find them or not.

I would also encourage you to look into automated testing anyway even if it's technically not part of your job, many manual tests can be automated eventually and it would be a matter of time before someone else finds out. Manually testing something that can be scripted is low end work. I get that you are also designing the tests yourself, but I think you can improve and show your value to the company by slowly moving away from manually executing them and making that an automated process. It depends on the company of course, but most companies value people that want to improve themselves and make their job easier (and cheaper/faster).

In addition to the other answers, it would seem important to me that you find out IF you are actually letting bugs slip through. The way you write this would make it seem the software is up and running in production, so surely if there are bugs they would be reported. Then you can check if you should have been able to find them or not.

I would also encourage you to look into automated testing anyway even if it's technically not part of your job, many manual tests can be automated eventually and it would be a matter of time before someone else finds out. Manually testing something that can be scripted is low end work. I get that you are also designing the tests yourself, but I think you can improve and show your value to the company by slowly moving away from manually executing them and making that an automated process. It depends on the company of course, but most companies value people that want to improve themselves and make their job easier (and cheaper/faster).