I guess the #1 results in:

(((A & B) | C) & D) | E

doesn't it?

My method for simplification:

(1) Start with the outermost operator and move it to the start of the expression.

"(A operator B)"  becomes  "operator (A B)"

(2) Repeat step 1 for each sub expression with an operator to move.

"A operator (B operator C)"  becomes  "operator A (B operator C)"  then "operator A (operator B C)"

(3) Remove all brackets.

"A operator (B operator C)"  becomes  "operator A operator B C"

So for my example:

( A or B ) AND ( C or D or E )

First simplification:

AND ( A or B ) ( C or D or E )

left side

AND ( or A B ) ( C or D or E )

right side outer

AND ( or A B ) ( or C ( D or E ) )

right side inner

AND ( or A B ) ( or C ( or D E ) )

remove brackets

AND or A B or C or D E

In Odoo domain syntax this would be:

[ '&', '|', (A), (B), '|', (C), '|', (D), (E) ]