Improve Link UI anchor position in Navigation block submenus

[getdave]

What problem does this address?

When creating menu items within submenus within the Navigation block the Link UI popover will remain open after the link is created. This is intentional in order to allow users to then adjust the settings of the link (e.g. Open in new tab).

However, the popover can obscure the + button inserter.

What is your proposed solution?

Either

• improve the anchor positioning of the Link UI so that it takes into account the submenu (note there was work to do the same for the block toolbar recently).
• hide the Link UI following creation - note however that this would require another click to modify any link settings. User feedback was that this was suboptimal so we should be careful before changing this behaviour.