How to align symbols at start of equation?

Questions
1

Consider the following formula:

$
&(P and Q -> R) or not(not R -> S)  \
equiv^"Impl. Elim." &(not (P and Q) or R) or ((not not R) or S) \
equiv^"De M." &(not P or not Q or R) or ((not not R) or S) \
equiv^"DNE" &(not P or not Q or R) or (R or S) \
equiv^("Idempotenz" or) &not P or not Q or R or S \
$

test
test438×251 42.2 KB

I would like the $equiv$-symbols to be aligned, not the text above it. Ideally, all $equiv$-symbols would start at the same vertical line. The text above would still be centrally aligned, going into both directions. The formulas could then be re-aligned in the current way.

Two alignment points alone don’t seem to help:

Summary 
$
&&(P and Q -> R) or not(not R -> S)  \
&equiv^"Impl. Elim." &(not (P and Q) or R) or ((not not R) or S) \
&equiv^"De M." &(not P or not Q or R) or ((not not R) or S) \
&equiv^"DNE" &(not P or not Q or R) or (R or S) \
&equiv^("Idempotenz" or) &not P or not Q or R or S \
$

test
test438×251 42.3 KB

What is the best way to achieve the intended layout using Typst?