Open loads a dialog template from a file and Open from clipboard loads a dialog template from the clipboard. From the What's New Webpage:
"The Dialog Editor now loads and parses dialog templates without the assistance of the
WIL interpreter DLL. Substitution is no longer performed on template string literals and
the substitution syntax is preserved when embedded in the dialog's title, or a control's
name and text attributes.",
"It is possible to still load templates into the Dialog Editor using the WIL interpreter
DLL by using one of the two new File menu items:
Open with WIL - Loads a template from a file with the assistance of the
WIL interpreter DLL.
Open from Clipboard with WIL - Loads a template from the clipboard with the assistance
of the WIL interpreter DLL.",
and
"When these two menu options are used, substitution is performed on the dialog templates
so any substitution syntax will not be preserved when the loaded template is
saved to the clipboard or a file."
From the somewhat sparse documentation in the help:
https://docs.winbatch.com/mergedProjects/WinBatch/WINBATCH_F__002.htm