Undo actions or unmark as completed in Training Plans

Hello! I'm new to the watch and the app, but I found this one action or better said the inflexibility of the actions in the training plans to be extremely frustrating. I signed up for the Garmin Coach Half Marathon and did the benchmark run and another run as scheduled, but the 3rd run I mistakenly started from the Activitires-> Run and not the Week X -> X Run and it did not registered in the Training Plan for my Half Marathon Plan. In the process of adding it there and move on to my next workout, I accidently marked the entire Training Plan as completed and now have to start it all over again because I am unable to unmark it as completed. 

So I need two things: 

1. the possibility to add any running activity to my weekly plan so that i can receive the plan for the next day or week 
2. just be able to mark AND unmark a weekly activity as done in the weekly calendar and mark OR unmark the whole training plan as completed whenever I want

It's ridiculous that i cannot perform either of these actions right now, at the level of maturity at which the brand Garmin is currently!