For myself, it's incredibly rare for me to have a starter and a main and a pudding, far more usual to have 2 of 3 courses. However, as such meals are usually very drawn out, and there's often some uncertainy about how long courses will take to arrive, I am happy to inject at beginning of meal or before main (if I've chosen a low carbohydrate starter) - and have extra if I make a late decision for pudding.
In practice, I find such meals tend to be at wedding receptions (or recently, family meal for parents' 50th wedding anniversary). I find the whole experience of weddings very difficult to manage, as there's often a drive between church and reception venue, I always have to drive as partner doesn't, choice of low sugar non alcoholic drinks is often very limited (I don't drink any alcohol if driving), meal times are often uncertain, and at large gatherings (we have a big family), it takes ages for all to be fed, plus injecting discretely through a dress is more difficult, so I prefer a smwart trouser suit and always press the injection whole to prevent blood leaking out onto pale fabric.
So, for the once a year or so, I just accept that I will run slightly higher than ideal blood glucose levels for the day. And find reasons not to attend as many weddings as possible 🙂