Snippet

Select the text:
[aaa]

Use this snippet: ${0:${SelText/.(.+)./\1/}}

Now the selected text is:
aaa

Press { key.

Now the text is:
{aaa}

Undo.
** Now the text is:
[aaa]

I think it should be:
aaa

Similar to the 1st post,

Enable “Auto-Complete Brackets/Quotation Marks”.
Select “ABC”.
Use this Snippet: ${0:${SelText}}$0
Now the Text should be “ABCABC”. And the left “ABC” is selected.
Press “(“.
** The selected text is erased by “()”.

1:
Go on with the last example above:
Do the steps and Undo once.
** The result is not correct.
It should undo the “()” only.

Another example:
Select “123” and run this snippet: ${0:${SelText}}$0
(Now it should be “123123” with the left half selected.)
Press Left or Right key.
Type “xxx”.
Undo.
** An “x” remained.

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2:
Should be able to quit the snippet inputting mode by pressing Esc key.

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3:
Select “xxx” and run this snippet: ${1:?}${2:${SelText}}$1$0
By pressing Enter key I wanted to insert a new line before and after “xxx” but failed.
Is it possible to make it support new lines in such cases?