Hi @Otium - welcome!
If you want to ‘plan’ around a specific ride/workout, then you can use the Pin feature to pin an activity/workout and then clicking Adapt Forecast will let Xert adjust your training around your planned activity. This can be helpful for incorporating things you enjoy into your training program like hard group rides, weekly time trials, or races.
Check out this thread for a How-To guide on adapting your forecast around planned activities.