LaTeX.org

A solution that works under ubuntu bionic:

Go to:

https://launchpad.net/~lyx-devel/+archive/ubuntu/release

and follow the instructions to install the ppa to your software sources.

Then do:

sudo apt-get dist-upgrade

and enter Y to install LyX version 2.3.6.1

Then reconfigure your menu and ...

I have a large number of LyX documents that use bibliographic references.

Each reference is labelled with a key and a label.

Clicking on the gray box pops up a window where the key and label may be altered.

I almost always have connected multi-word labels with underscores, for example:

a_multi ...