Thank you for taking the time to craft a very detailed answer.
I am logged in as the main user, but my accounting module isn't showing the localization section and I am not able to proceed beyond that point. In my view "taxes" sits just under the "chart of accounts" item in the Accounting section, under the configuration menu item on the Accoounting modules main navigation. I have a vague memory of having at some point looked at the localized charts of accounts , in a view quite similar to what's under apps, but at this point, (with so close to mentally just breaking down :-) ) I really cant be certain what I have seen/accessed and what I am simply imagining.
We are running a multi company set up (Odoo 15.0-20220511 (Community Edition)) , and I have been trying different ways of accessing this, from parent company and a "regular company", with and without developer mode activated and so on, but keep hitting a wall.
**Edit**
I have a test environment set up that at least at somepoint was identical. In the test environment I under Settings module >> Accounting I can see "Fiscal Localisations" - for some reason this isn't visible to me in my live environment , I can also see some other minor differences in the options I am able to access. For example, in my LIVE environment the option to select a value from a dropdown called "Fiscal Country Domestic country of your accounting" is not available