There's no drop down box, but there are 2 boxes with arrows at each end. Sadly, they only change the type of grass available.
You have got me stumped. What you are describing is not the Edit Effect Layer behaviour that I see in Trainz Plus and in TRS22PE.
If you open the Edit Effect Layers option from the Surveyor Edit menu and there are no effect layers already installed then this is what you will see..
The top box is a text entry box for the name of the new Effect Layer you will create. The second is a drop down list.
Click inside the second box to select the type of effect layer. This will produce the following list...
If Effect Layers already exist in the route, such as one you just created, then if you open the Edit Effect Layers option from the Surveyor Edit menu then this is what you will see..
To select a layer click inside the top box containing the name and select a layer to edit or delete.
To delete a selected layer lick the little "
x" icon with the red dot.
To add a new layer click the "
+" symbol.
To save the layer as a Preset, click on the small disk icon.
To edit the selected layer click on the small round switch button next to the disk icon.
If none of the above is happening in your Trainz Plus then the best advice I can give is to contact the HelpDesk (the
Support link at the top of this page).