It is possible to view custom variables as a column in Listviews.
First, we need to create a custom variable (see manual, https://www.op5.com/manuals/index.html#page/op5_Monitor_Administrator_Manual/op5_monitor_configuration_tool.html).
To create a column in listviews for the custom variable go to Configuration -> My Account
Add the following to "table host" or "table service"
The in the example above we use the custom variable "_ASSETID".