nightTab v4.0.0
Firefox v70.0.1 on Win10
Issue: Block style Bookmarks that have names that span two or more lines (the tiles have to be tiny enough for it) don't follow Content alignment settings properly (Bookmarks > Bookmarks > Content alignment).
In fact, they go in reverse:
Left aligned

Right aligned

The Calendar tile is following the settings properly, the Send tile is going in reverse. Only happens when "Align contents horizontally" is selected.
Nothing like CSS bugs early in the morning 馃槃 Thanks for the report. I'll get a fix ready asap.
Updated to v4.1.0 and

too much justification.
There's also a bug with breaking bookmark names with multiple lines in a way, that they fit their box:

When I change the CSS at .is-link-item-display-name-show .link-display-name from display: block; to display: contents;, it works:

Besides: Thank you for the new feature! Exactly what I intended.
Edit:
Firefox 71.0 (64-bit)
NightTab 4.1.0
I've been testing a few fixes to this. This component makes heavy use of flexbox to achieve the customisation of the alignment and order.
Experiments:
The current version with flex-basis: 1% on the name:

Gives us predictable alignment but does not allow for text (with multiple words) length to grow.
A test with no flex-basis (so a default of flex-basis:auto):

But allows for scenarios where, if the name string with multiple words is just long enough to break onto new lines, a large gap can appear:

It does seem there is no simple solution to this problem as both flex-basis: auto and flex-basis: x% have downsides. So for now I will remove the explicit flex-basis declarations. This at least _seems_ to have fewer downsides.
The gap is much more preferable to some tiles getting aligned in reverse order, this is more consistent. Closing the issue. Thanks for explaining the options in detail.
Most helpful comment
There's also a bug with breaking bookmark names with multiple lines in a way, that they fit their box:
When I change the CSS at
.is-link-item-display-name-show .link-display-namefromdisplay: block;todisplay: contents;, it works:Besides: Thank you for the new feature! Exactly what I intended.
Edit:
Firefox 71.0 (64-bit)
NightTab 4.1.0