Spacer block can only be expanded horizontally in navigation block submenus

[talldan]

Description

The spacer block can only be expanded horizontally in navigation block submenus. It seems like it should instead work vertically—the same orientation as a submenu.

Step-by-step reproduction instructions

1. Add a navigation block (horizontal)
2. Add a link and create a submenu with some more links
3. Try adding a spacer to a submenu

Expected behaviour

The spacer can be used to space out links in the submenus

Actual behaviour

The spacer can only be used to make the submenu wider

Screenshots or screen recording (optional)

[annezazu]

Seeing as the spacer block isn't included in blocks allowed for the navigation block after the ligher navigation work #34041, does this issue still make sense to leave open?

[talldan]

It's a long story!

Spacer can still be added to the nav block, it has to be added via the Global Inserter like other non-link blocks. It can't be used in submenus anymore by the looks of it, but it can still be used at the root of the nav block in a vertical layout.

It looks like the issue is fixed though since #36340. So I'll close this.

It's worth mentioning that the row block still has the same bug, you can't space items you can just make the row taller. That's described in #36197, so it still seems valid to close this issue.