Indeed, it is worth on a normal flight to observe the FMGS phase switching to start with.
If you select the PERF page, you will see the big title at the top of this page = FMGS phase. Certain logics and subsequent mode activation (as toga selection) are related to fmgs phase.
Now, more complex, same question as Tyro above post, but with flaps 1 ?
...here there is a trap or 2 answers possible I believe...
We can discuss it further after your posts.
Flyer146