Code:
<li class="nav-item"><a class="btn btn-outline-secondary bg-inverse btn-sm">Support</a></li>
<li class="nav-item"><a class="btn btn-outline-secondary bg-inverse">Log in</a></li>
<li class="nav-item"><a class="btn btn-outline-secondary bg-inverse">Sign up</a></li>
Screenshot:

Expected output:
It should align vertically and doesn't. Not sure how to write it, couldn't find docs for this.
cc @mdo
Can't say I understand why you'd want to mix button sizes within a navbar like this in the first place.
I wouldn't assume mixing as much as option to use smaller buttons in navbar instead of default ones for cosmetic reasons/or to fit more in case of apps.
Correct @rafalp exactly
Not to mention logos. The default navbar height is a bit small for a site logo.
In general, I'm in support of easier vertical alignment of navbar contents :). I'll take a look soon.
:+1: The docs also mentions ".navbar-nav for a full-height and lightweight navigation". I'm not sure what "full-height" is supposed to mean in this context.
Small example of using utilities to tweak this added in #19890.
My wish for being able to use a larger logo and have a vertically centered nav inside the same navbar does not seem covered by this. Should I open a separate issue?
@fuzzy76 For that, you're likely going to have to use custom styles to account for the larger image. In our default, non-flexbox version that's rather difficult to account for in a generic sense.
Most helpful comment
In general, I'm in support of easier vertical alignment of navbar contents :). I'll take a look soon.