Just to correct one misunderstanding: you can't insert the microSD without removing the SIM card because the two share the same slot. But they share it, so you can put the SIM back in together with the microSD. It's only a problem is you have a dual-SIM model and actually want to use 2 SIMs (because for those models it's 1 SIM + 1 microSD or 2 SIMs).
But yeah, Samsung don't do adoptive storage (i.e. formatting the card as internal), or certainly not on their flagship models. Nothing you can do about that. There may be older-style kludges available if you root the phone (if you can root the phone, and if that won't stop you doing something else that's important to you). Otherwise the one thing you can do to increase storage is to fit a microSD card and move other stuff to it: media storage is what the card is intended for, so photos, videos, music etc can be moved, which will free up space for apps (especially videos, which eat a lot of space). Of course that assumes that these occupy a significant amount of storage on your phone - it won't help if they don't. You may be able to partially move some user-installed apps to SD anyway (Settings > Apps (or App Manager), select an app, look for a "move to SD" button). But that only moves part of the app and doesn't move the app's data, and not all apps support it, so it's impossible to say from here how much this will help you.
Other that using a microSD card in one of those ways, the only way to boost space is to remove stuff you don't need from the phone.