Solved
https://www.geogebra.org/m/p4cmtaht
red line g show label (label was hidden after uploaod ) and move label to new position
===>
changes CAS line 1
line g definition was overwritten by Algebra View style of line g
total app crash due to loss of definition of g in CAS
see also CAS line 17, line 20
rendering of input line: Variable Name was replaced by value of variable - flatten removed
A_H:=Transpose({Flatten({Vector(A),1})})
makes it very hard to read!
The same problem 
Sorry, I don't see label "g" here - so I can't drag it https://www.geogebra.org/m/p4cmtaht
as i said, the label has been hidden after uploading, but i edited the app to show the label for you.
you may also look to https://www.geogebra.org/m/y9xhyysv
BTW
edit the app in place of activity the height in advanced setting often changed due to rearrange the app window elaborately
Sorry, still don't see label "g"
Sorry, but I cant move it to better position, because...
And live show
Open https://www.geogebra.org/m/p4cmtaht
Drag g's label
-> seems OK. Do I need to do anything else?
OK, so all you need to do is type
then drag label
I can't do anything in CAS with the form g:=X=(0,0,0) + t (0,-1,3)
any dependig calculation will crash.
Do realy think moving a label should make changes in CAS, I can't believe it!
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