Chest

You sure can!

You can add custom exercises this way:

Home screen >
Exercises (bottom icon) >
Custom (top right nav) >
Add my own

You can swap in the exercises you like using swap feature (http://drmuscleapp.com/news/swap/).

If you prefer to create a totally custom workout, you can do it almost the same way:

Home screen >
Workouts (middle icon) >
Custom (top right nav) >
Add my own

Next, you can order your workouts into a program this way:

Home screen >
Workouts (middle icon) >
Custom (top right nav) >
Programs (top right nav, 2nd row) >
Add my own

Simply put, the steps and structure are: exercises > workouts > program.