I think so, this is for simulation purpose. You also need a symbol view for your schematic, which points to your trenchmimcap model.
If you wish to run DRC & LVS, you have to update the corresponding files, which needs to understand their syntax. If so, update your DRC file to find and check the new layer (min/max dimensions, spacing to other layers ...), and update extract rules in order to find (recognize), extract and check the trenchmimcap's dimensions and compare it to its schematic properties. You also need an LVS view (copied symbol view, I think).
If you always use the same trenchmimcap cell, you can suppress its full extraction/check by using a corresponding view order in the extraction stop list. And for DRC you then just need to check the min. spacing to other layers.
Get the necessary views by copying e.g. the mimcap views, and change them to your trenchmimcap name & properties.