Hi

You can edit a shortcut to be one that you would find useful and pin it to the new tab page so that it does not change. This support article should help:

https://support.mozilla.org/en-US/kb/customize-items-on-firefox-new-tab-page

I know, I already did that but I want to disable that auto adding feature, because sometimes I change that pinned shortcuts but as I mentioned in the post, even when the items on the screen are finished, they keep appearing in front of me, so it is just waste of time trying to delete them. I want to customize that place as I want, and I think it is negative for firefox to not add that feature.

The people who answer questions here, for the most part, are other users volunteering their time (like me), not Mozilla employees or developers. If you want to leave feedback for developers, you can go to the Firefox Help menu and select Share ideas and feedback…. Alternatively, you can use this link. Your feedback gets collected by a team of people who read it and gather data about the most common issues.

You can also file a bug report or feature request. See File a bug report or feature request for Mozilla products for details.