There are strong ‘beliefs’ on the entry and exit points of 5a but there are three potential entry and exit points and therefore a total of nine combinations of entry and exit. It’s impossible for anyone on this forum to state with certainty which combination was used.
The objective of the perpetrator would help explain some things except we don’t know that either. For example, if the objective was to abuse MM in situ then IMO this gives more credence to the open window to see/hear suggestion.
Another important factor is if the perpetrator acted alone or not. Again, IMO the window is a good exit option for a two person abduction.
Based on logic and a planned abduction by one perpetrator - HCW has suggested CB acted alone, my opinion is that the entry was the patio doors and the exit was the front door. It makes sense that the perpetrator was watching the apt so waiting until a check by a parent had been made and the coast was clear, entering through patio doors is the most efficient method. The window was opened as an emergency exit, particularly important if the objective was in situ abuse as is part of CB’s MO in prior known cases. The exit via the front door is the farthest exit point from the Tapas Bar and the quickest route a waiting car or walking ‘safe’ zone.