@toinewx you can use Xcode you just have to be really careful about:
- what target membership you select - Xcode doesn’t have great integration with SPM yet to be able to make this easy, it just picks the first target it knows about which is usually a dependency
- where you save the file. If you save it in the wrong place then it will work up until you regenerate your project then you are going to get errors
See Server Side Swift with Vapor - Part 8: Models And | Ray Wenderlich - #7 by simonqq as an example for errors caused by this.
So in short it is certainly possible (and I do it half the time) but it can cause issues which is why I suggest to do it through terminal, especially while people get used to SPM 