ingredients span the whole row because in many (i dare say most) cases they need as much space as possible. however with some simple css (“padding-left” i would think) you can align it as it works for you)

there is no single file as such.
this is all dynamically generated via filters etc and if you were to simply edit rows/colspans/td etc directly you will most likely break things elsewhere sooner or later
honestly, use css to change/tweak layouts. after all, that’s what it’s for

>it is important that I have the ability to relocate that particular injection.
you could try to change
$markup_item['tr_add_ingredients'] .='<td colspan="'.($colspan).'">';
to
$markup_item['tr_add_ingredients'] .='<td></td><td colspan="'.($colspan-1).'">';
in wppizza-addingredients.php approx line 1684

though that’s at your own risk of course (and i still cannot see how this could not be accomplished with css, but i dont know every little detail of your setup of course)

> I also want to add identifiers to the injected code as outlined above. Examples being “TOPPINGS:” and “SPECIAL REQUESTS:”.
which you can if enable “Display ingredient groups in emails (sort and display ingredients by (custom)groups in emails, thank you page, admin history print)”

>support being minimal,
how is that “minimal” ?
generally support (free plugins or not) is for plugins as they are and not for making them do something they don’t or re-writing them for a particular scenario. that’s not support, that’s customisation.

even so , wherever practical/possible I’ll try to point people in the right direction even if it’s not inbuilt or at least leave some filters action hooks in them (i am also always more then happy to add some filters on request) (and see above of course)