Can anyone tell me how to centre a set of three dropdown menu buttons in the middle of the page with bootstrap studio 4+
On the list item with the class nav-item you could set the margin(s) left and right to "auto".
You can also just apply a spacing class "mx-auto" directly to the nav-item.
https://getbootstrap.com/docs/4.1/utilities/spacing/
If you are using Bootstrap Studio 4 and using a Bootstrap 4 setup on your site, then this is built into the menu now so there are actually settings for that in the Options pane. Not always the easiest to find. What you need to do is highlight the Nav tag of your menu so in the tree you will usually see something like:
Navbar ....Navbar Toggle ....Navbar collapse ........Nav
Click on Nav in the Overview pane on the left and you will see an Alignment options show up at the top of the options. Choose how you want it, left, center, right and you're all set!