AFAIK can't with 5.4

It's gonna come with 5.5 or 5.6

The Main AI System is separated from CryAction and GameSDK so it is certainly possible.
You may have to implement your own flavor of AI for your game though.
You can check out the Isometric Template for an example on Pathfinding available as a default C++ template from the CRYENGINE Launcher.

With 5.4 you may need to do a bit of coding really. Underlying systems for AI are there. Interfaces to use. But basically there'd be lot to write to get it to work as you want. In 5.5 previews you have various AI components exposed that utilize ai system. If you really want to stay with 5.4, i suggest to go to 5.5 and see source code for those components like observable/observer, navigation and behaviour trees, and rewrite those that you need for 5.4, there shouldn't be much of a work. Component system hasn't changed at all.

They are defined in this file:
"C:\Program Files (x86)\Crytek\CRYENGINE Launcher\Crytek\CRYENGINE_5.4\Templates\cpp\IsometricPathfinding\Assets\Scripts\AI\Navigation.xml"

You can, though this can be come a very complex subject depending on how detailed and how you want to implement this feature.
You may want to take a peek into the GameSDK Cover system for ideas on how this was done originally.

A cover system such that AI hides behind objects, would most likely be too specific for an engine component.
More likely, the new Schematyc and/or systems will allow the user to create this functionality in their desired fashion.

I am not sure which algorithm is used in the current Cover System implementation I'm afraid.

Check out the FPS template, its a physics on-collision event AFAIK

Well on the collision event you can check if the colllided-thing is a player.

Perhaps this thread can help you out?
viewtopic.php?f=14&t=1527&p=6239