Edit: I initially submitted this as a feature request, but testing this again, I noticed it is already implemented. But it simply doesn’t work every time. I don’t see any pattern why it sometimes fails.
When closing tabs that are made smaller due to the space in the tab bar used up by multiple tabs, the remaining tabs shouldn’t be resized until the mouse is moved away. This makes it easy to close multiple tabs with the mouse without having to move the mouse to the next x button because everything has shifting after closing one tab.
Right now the tab closes and all other tabs resize due to more space in the tab bar. That means that the x button of the next tab won’t be under the mouse pointer and in order to close it the user has to move the mouse. This happens for every tab until the tabs are their maximum size.
This feature is already default behaviour of all other major browsers, at least Chrome and Edge and I’m pretty sure Firefox has this too.