Hi Ebonixs,
It's not possible to save the ATLAS format in Standard edition.
Did you try the 'Atlas' button on the toolbar? I tried it just now in L3DT Standard 2.6 beta 2, and the Atlas export worked without problems. The user-guide for the Atlas exporter is here:
http://www.bundysoft.com/wiki/doku.php?id=plugins:fileio:l3dtio_atlas2
You can export 'unique textured' Atlas terrain from L3DT Standard, with heightmap sizes and texture sizes up to 2048x2048 pixels. You cannot export 'blended texture' Atlas terrain from Standard; for that you require Professional. Please follow the
instructions on this page if you would like to receive a free trial of L3DT Professional.
Cheerio,
Aaron.