Indeed, I’m looking forward to the release 
Exactly, the source are both host parameters (manually maintained) and custom facts. To give an idea, here’s the list of :content: rows of the foreman_column_view configuration:
:content: facts_hash['uptime']
:content: params['location']
:content: params['room']
:content: params['rack']
:content: params['bay']
:content: params['comment']
:content: params['commissioning_date']
:content: facts_hash['rtcwake_alarm']
:content: facts_hash['rtcwake_alarm_time_human']
:content: facts_hash['rtcwake_wish_time_human']
:content: facts_hash['dmi::product::serial_number']
:content: link_to(_("Console"), "https://#{host.interfaces.first.name}", { :class => "btn btn-info" } )
:eval_content: true
:content: facts_hash['reboot_required']
:content: facts_hash['reboot_required_pkgs']
:content: facts_hash['reboot_required_since']
Since “custom” is by design “custom”, what I’d love would be the possibility to add custom cards with custom rows, with simple “label” => “value” pairs, similar as to what foreman_column_view was doing, but with the possibility to add cards to group this information.
For example, I’d then create a location card, which contains the location, room, rack and bay host parameters we maintain manually, maybe extended with network facts like to which switch-port a machine is attached (via custom facts).
I’d similarly create a card with reboot information and rtcwake information, for example. To give an idea, the rtcwake data is populated by calling rtcwake -m show, and we manage RTC wakeup times with Puppet to conserve energy for machines and wake them up at specific times (with a very large variety of desktops, this works more reliably than Wake on LAN).