Loosing data with back end registrants

I have an event with multiples list custom fields. All options are quantity limited. The 2 first pictures show user data from database
and backend registrants Form. We could see a difference on Session 2 PM.





The problem is :
EB will not show an option if this one is full (quantity value reach is max value). This way of doing it could be ok on front end Form. But in back end form : No!

If a back end user modify 'Session 1 AM' value... What is gonna happen after saving? I will loose 'Session 2 PM' value.

I suggest :

-In back end registrants Form, all value should be show. For quantity value field, find a way to tell back end user that option is full ?

-In front end registrants Form, a quantity value field should be or not visible (setting option?). If it's visible and full, make it not accessible but show it (when an option (or field) is hidden, we got email from user to support them : "I can't find the option". Dear customer, the field is hidden because it full ...

Others pictures :