I just see that this is a frequently discussed option and what I see is that this is rejected so far due to the reason that it might be unclear which pattern should be displeyed in case there are more than one pattern actively played in the song at one time.
BUT: This is really seldomly the case from my point of view and for a 'playalong' or to check a song it would be great to have this, really!
I would suggest the following solution and kindly (and strongly) enquire this to be developed:
If there is not more than one pattern played at a sequence of a song, offer a toggle to always follow the recently played pattern in the song!
If there is more than one pattern
a) as default select the first pattern from top in the pattern list (on the left side)
b) offer an option to let the user set a mark in the songpattern (option-button-like) which one should be shown
THIS WOULD BE SO HELPFUL!!