That’s the problem; you are up-to-date.
Specifically, and you can find this at the M2E wiki, earlier versions of M2E showed nondeterministic behavior when operating alongside the rest of Eclipse, and the developers removed some features from it. These include things like the plugins tab, and support for adding plugins through wizards. Now, you have to edit plugins and pluginManagement sections by hand. Even then, to execute the plugin, you shall need to resort to the command line.
If somebody has created a “project configurator” for the plugin, and you have installed that configurator into Eclipse, then Eclipse will be able to run the plugin as earlier versions did. These are called “m2e connectors” or “Lifestyle Mappings” in the Eclipse Marketplace . You can reach that fast by Preferences|Maven|Discovery|Open Catalog. But, few connectors exist, and none for Liquibase.
It therefore falls on the Liquibase developers to write such a connector, sadly. I don’t know how to do it.