You would need to construct a list/array to pull from... Although I would recommend accomplishing what you are attempting using a single maple call (why have 2???).
To fix what you have:
$selector=range(1,5,1);
$TA=maple("
option1:=geom3d[point](P1,[5,2,1]):
option2:=geom3d[point](P2,[4,0,-4]):
option3:=geom3d[point](P3,[1,1,1]):
option4:=geom3d[plane](E1,[P1,P2,P3]):
option5:=geom3d[Equation](E1,[x,y,z]):
[option1,option2,option3,option4,option5];
");
$LE=maple("$TA[$selector]");
A BETTER WAY that is more efficient (single maple call)....
$selector=range(1,5,1);
$TA=maple("
option1:=geom3d[point](P1,[5,2,1]):
option2:=geom3d[point](P2,[4,0,-4]):
option3:=geom3d[point](P3,[1,1,1]):
option4:=geom3d[plane](E1,[P1,P2,P3]):
option5:=geom3d[Equation](E1,[x,y,z]):
listOfAll:=[option1,option2,option3,option4,option5];
selected:=listOfAll[$selector];
[convert(selected,string),convert(listOfAll,string)]
");
$theChosenOne=switch(0,$TA);
$theRest=switch(1,$TA);