Hello,
I wonder if there is any way to modify the engine for the launcher doesn’t open automatically when I open my project.
I think that if you go into the launcher and click launch it will open the projects menu, then you can go to the bottom of your screen and right-click the U symbol tab(unreal engine) and click pin to task bar or something like that. Im assuming you have windows???
But instead of the launcher you will have the unreal project opener open
yet, the launcher will also open. 
If you open the project through the .uproject file, it will also open up the launcher. You can simply close the launcher while it is loading. It won’t effect your project.
The launcher only stops opening if you are using a C++ project and open it up with VS to compile it.
In other words you can’t do a thing about it
It’s sad that you’d have to modify the engine to get this. However I can understand that they need to make sure to show you that there is a new version available. A project first, delayed start of the launcher, would be much appreciated though.
It doesn’t hurt that you get to see their other latest products. A launcher isn’t required to help keep developers up to date. Unity manages fine with a simple, project focused launcher, that anyone can easily opt-out of to directly load the most recent project. The editor itself checks for updates and alerts you if there’s a new version. The launcher is entirely for our convenience.
It inconveniences us, however, when the program is riddled with bugs and the only solution is to open up the Editor directly with admin privileges. That’s why I’m on this old thread.
Amazing engineering design. This was probably advised from the marketing department to get more exposure. I never need the launcher, just for updates. Period.