Thank you. That tutorial was very helpful.

I had actually looked at UseAttachment() but wasn't sure how it applied.
I did have a problem with the image names, though. The GMap.NET generated image names are very long with spaces and underscores in them. Using the raw name failed, but changing it to ...

My problem was the image file name. GMap.NET generates file names that look like: 'GMap at zoom 16 - ArcGIS_World_Topo_Map-638114443481562529.png'.
Using that file name failed.
Changing the name (of the .png and .pgw) to something like 'mymap1.png' worked.

Ugh. I am not able to load overlays.
Version: Command PE - Premium Edition v2.1.12.1

I understand the steps:
* create attachment
* Get the ID of the attachment from the folder name
* Create a trigger and action that calls ScenEdit_UseAttachment('GUID')

I even tried running _UseAttachment() in the ...

I took a look at getting SAS.Planet, but it is super sketchy looking. The download sources were flagged as dangerous.

Do I have to re import them every time?

Yes, I believe custom layers have to be manually loaded every time you load the scenario or a save of the scenario.

Ugh. There's no Lua script that can be used to load custom layer images?
Having to be manually loaded each time a scenario is opened ...

Next question: Is it possible to make a layer part of a scenario? i.e. To load a layer at the start of a game - or maybe even in response to an event? (A quick look through the Lua docs didn't turn up anything obvious.)

New user of C:PE. I wound up here from following the link in the manual.

Never mind. I see that it created the files on the desktop.