This guide will tell you how to farm for Healing Return in Warframe. Go through the guide and follow the simple steps to farm it.
Healing Return can drop from normal infested crawlers, which can spawn in just about any infested mission on any planet/Node. It is recommended to run endless missions (primarily survival) to farm crawlers; Nekros also helps if you have him.
You have to stay for at least two reward rotations before extracting in the endless missions, as that gives the crawlers a decent amount of time to spawn so you can get to kill a decent number of them before leaving. Though it’s up to you how long you stay in the end. This mod has an extremely low drop rate, so you’ll likely be farming for the mod for quite some time.