Thank you all for your replies. Yes, I was trying to do that (having 2 tables), but as I was saying, "changing the internal table data linked to the table control is a mess, especially when the user changes the data of a line when filter is on".
The reason is that lines don't have a key that I could use to update the right "backup" table line when a displayed line is modified by the user.
So what I did (or more precisely what I am doing now) is to add a key field to my internal table.
But everything would be MUCH easier if I could just make lines invisble in Table Control, but apparently it is not possible, isn't it? (SAP guys, if you hear me 
)