Hi - I am sorry to hear about your needy knees! Ouch. What does your doctor say? If you haven't seen one, it may be your best bet. But, if you want my thoughts, here goes!
Let me start with a bit of background stuff: Lotus is one of the postures I define to be “high risk/low reward., I have written about its dangers elsewhere, and you might enjoy this article: Lotus Pose: Destroyer of Disease, or Destroyer of Knees?
. If you want to continue trying Lotus, I would ask “why?, What would be your intention is doing that pose?
If your intention in all the external hip rotation postures you mentioned (Swan, Lotus, etc.) is to increase your range of motion in external rotation (which is often referred to as “hip openers,, although this also could be used to describe increasing abduction range of motion), then the next important investigation is to ask yourself “What stops me?, What prevents you from going deeper in those directions? If the answer to that question is tension, then there may be value in trying to go further, but if the answer is compression, then you have reach the limit of what your body can give you and there is no point or benefit in trying to go further. Sure, you can still do these poses to keep what you have and gain the other benefits of your Yin yoga practice (mindfulness, energy work, etc.) but once you feel the bones hitting, don't try to go further.
With all that as prologue, let's look at your main question: your knee is injured. When should you go back to postures that stress it? I would say-wait until there is no pain! Yes, let your knee heal. Again, what does your doctor suggest?
I can speak from some experience that it takes a while for the knees to heal, depending upon what you did to it. You can, indeed, tear your meniscus and ligaments while holding a pose even for a minute! And, it may take surgery to repair it. These tissue can be very slow to heal. You can read about my journey in this Yin Yoga for the knees article
and via this Forum thread
. And, here is another thread
on a particular yin sequence for the knees that you might find helpful.
So, lots for you to study up on. Let us know how it goes!