I've divided it into verses and added two words to line 8. I quite like the fact that there are rhymes but they are fairly restrained, shy - perhaps - like the mist.  Though the image of the shy mist doesn't work completely because it would be the person/thing drawing back the mist curtain which is shy, not the mist itself.  But I think we can leave that for any really analytical reader to worry about.

The sea is visible again;
the mist rolls back -
but shyly. We see
not as through a glass darkly
but through suburban lace.

We make out what we can:
the headlands, the islands and
a shapeless mark, a place
on what would be the horizon.

Things we know are there:
The islands and the capes
But which will not be revealed
Before the dark comes on
With blackout drapes.

The Case of the Disappearing Writer!    Yes, other things took over and the poem was put on the very back of the furthest burner for a while.  However, we are now switching on the gas and striking a match. Will there be a small explosion or merely a splutter? 

We make out what we can:

the headlands, the islands and

a shapeless mark

on what would be the horizon.

Things we know are there

The islands and the capes

But which will not be revealed

Before the dark comes on

With blackout drapes.

I've inserted the line about the islands and the capes both to explain what it is we might be seeing if we could and to provide one rhyme with the last line which makes - I think - a more satisfying ending.  I have also inserted 'which' in the third line from the end.

There's a satisfying rhythm to the words as they came to me.  But how - if at all - to punctuate them?  This is only one possible layout:

The sea is visible again;  

the mist rolls back -

but shyly. We see  

not as through a glass darkly

but through suburban lace.

The effect of lace curtains like mist  (and vice vera) is what I want. The next part I'm not so sure about.

We make out what we can:

the headlands, the islands and

a shapeless mark 

on what would be the horizon.

I found some notes jotted down earlier in the year. These might serve as a place to begin.

the sea is visible again    the mist rolls back

but shyly. we see   not as through a glass darkly

but through suburban lace   make out what we can

the headlands, the islands   a shapeless mark  on what would be the horizon

things we know are there but will not be revealed

before the dark comes on with blackout drapes.