I have enabled Related Assets, is it possible to make this required or added by default?
For SolarWinds Service Desk (SWSD), the short answer is: No, there is no native "Mandatory" toggle for the Related Assets section like there is for a standard custom field.
However, you can achieve your goal of ensuring assets are linked to tickets by using a combination of Forms, Custom Fields, and Automation. Here is how to approach it:
Since you cannot make the "Related Assets" section mandatory, the best practice is to create a Custom Field that acts as a gatekeeper.
If you want an asset to be added "by default," the Service Catalog is your best tool.
SolarWinds has a native feature that helps with "added by default" behavior without you having to build anything: Owner Mapping.
If you don't want to bother people at the start of a ticket but want to ensure the data is there at the end: