Found it.

TeX was not selected in the language menu.
( SciTE doesn't check mark the selected language so I didn't spot it at
first )

However now, when compiling I get ...   :O)

>texmfstart texexec --lua mini01.tex
TeXExec | processing document 'mini01.tex'
TeXExec | no ctx file found
TeXExec | tex processing method: context
TeXExec | TeX run 1
TeXExec | writing option file mini01.top
TeXExec | using randomseed 1346
TeXExec | tex engine: luatex
TeXExec | tex format: cont-en
LuaTools | using format name:
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/formats/cont-en.fmt
LuaTools | no luc/lua with name:
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/formats/cont-en
LuaTools |
LuaTools | runtime: 0.014 seconds

TeXUtil | unable to locate mini01.tui
TeXUtil | shortcuts : 0
TeXUtil | expansions: 0
TeXUtil | reductions: 0
TeXUtil | divisions : 0
TeXUtil | loaded files: 0
TeXUtil | temporary files: 0
TeXUtil | commands: 0
TeXUtil | programs: 0
TeXUtil | tuo file saved
TeXExec | TeX run 2
TeXExec | writing option file mini01.top
TeXExec | using randomseed 1346
TeXExec | tex engine: luatex
TeXExec | tex format: cont-en
LuaTools | using format name:
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/formats/cont-en.fmt
LuaTools | no luc/lua with name:
/opt/context/tex/texmf-cache/luatex-cache/context/9d2177de8a31df158f21be632b7742b7/formats/cont-en
LuaTools |
LuaTools | runtime: 0.014 seconds

TeXUtil | unable to locate mini01.tui
TeXUtil | shortcuts : 0
TeXUtil | expansions: 0
TeXUtil | reductions: 0
TeXUtil | divisions : 0
TeXUtil | loaded files: 0
TeXUtil | temporary files: 0
TeXUtil | commands: 0
TeXUtil | programs: 0
TeXUtil | tuo file saved
TeXExec | runtime: 0.141179
>Exit code: 0

SciTE doesn't locate its own generated files.

Fascinating !

Alan