Notation`AutoLoadNotationPalette=False​​Needs["Notation`"]​​Notation[ParsedBoxWrapper[SubscriptBox["x_","i_"]]⟺ParsedBoxWrapper[RowBox[{"Indexed","[",RowBox[{"x_",",","i_"}],"]"}]]]
In[]:=
identity=Table[
x
i
0,{i,1,3}]
Out[]=
{
x
1
0,
x
2
0,
x
3
0}
In[]:=
Limit
Sin[
x
1
]
x
1
,identity
Out[]=
1
In[]:=
Limit
Sin
Sum[
2
x
i
,{i,1,3}]

Sum[
2
x
i
,{i,1,3}]
,identity
Out[]=

x
1
0

x
2
0

x
3
0
Sin
2
x
1
+
2
x
2
+
2
x
3

2
x
1
+
2
x
2
+
2
x
3
In[]:=
Limit
Sin
2
x
+
2
y
+
2
z

2
x
+
2
y
+
2
z
,{x0,y0,z0}
Out[]=
1