absolutely a newbie question about install/remove from YasT

If I install something from YaST, and decide I don’t want it after all, will it remove all of the extraneous (dependencies?) things it installed?
Sometimes it seems like hundreds of other things are coming along with the ‘checked’ items, and the items that the first check added to the YaST install.

No, it won’t. I ordinarily don’t worry about such extraneous packages remaining (space isn’t generally an issue), but if I really wanted to pay attention to what was installed, I might examine the last installed packages with something like

rpm -qa --last|more

The time stamps will help with what was installed around the same time. Then you can decide what else you might want to remove.