Posted too soon...
This needs you to be persistant. ie keep going until the desired outcome - calm, quiet and relaxed followed by sleep. You also need to be consistant - do the same things with the same expectations.
At 20 months i would do an in-cot version of rapid return. It would work in a bed too.
So into cot, hand on chest. What you are aiming for is that your hand is reassurance enough for baby to be still and quiet and then wait until still and quiet becomes relaxed which becomes sleep.
You are, however, a million miles from this. But having your aim in mind is important. Don't fall into thr trap of assuming that because she doesn't easily manage this, that the method isn't working. Any method needs you to be consistant consistent and persistant until it does work.
So lie baby down and you stay close. Cuddles on the bed or lent over the cot. You are aiming for still and quiet (not sleep at this point, just still and quiet). Any squirming against your hold, lift very slightly (a few cm) and lie back down.
This repeatative resettling is part of rapid return. Also develop a mantra which you repeat constantly. For example "sleep time now, we lie quietly at sleep time. Nan night".
Then at every noise, at every move, all the time - lift and resettle, hand on chest and repeat mantra. Initially you might continually be doing this without any calm gaps over and over for hours.
Over time and towards the end of any bedtime you will notice more quiet, still calm time after the resettle. Reaffirm tgi s is what you want with lots of eye contact, sleepy smile, "that's good" whispered and so on.
Once you get this quiet calm, so not seek to withdraw. Stay there, don't move and wait. You may go back to the resettle, hand, mantra cycle. You may move from quiet calm into relaxing - that is the next necessary state before sleep comes. Stay close, wait, positive eye contact.
On from relaxed comes sleep. Again stay there. You might be able to straighten up and move your hand away, but stay there. Put your hand back if reassurance is needed. Otherwise just wait.
Over time the idea is that the quiet calm comes more easily and resettles needed less and less often.