I have used a loop using sticky back copper trip off a roll that I stuck around the window with the two ends running down towards the floor behind the curtain . It is roughly 22 foot all in ( 8x3 window frame) with about 3 foot to the floor .. tuned 40 using a 945 atu and a couple of watts but didn't try other bands as it was on a monobander , worked EU with apparent ease ..
I havn't used it tx for a while as I thought maybe I was getting a little obsessed "needing" to run a radio in bed
but use it now and again to hook the TECSUN rx but to be honest the antenna on the rx works well as it is for casual listening ..
could you not drop a random wire over the balcony at night and load it against the balcony itself ? maybe worth a try , I have done ok in the past with a wire slung out the kitchen window to the bushes 20 odd foot away no higher than 5 foot with a counterpoise to the sink ..