For keeping potential recruits, when have a sheet selected I believe can just right click to lower it and then drop on desk, it should stay there til want to hire someone or throw it away. If you meant sheets of hired crew, to the bottom left of the desk is a drawer they go back into if done with them.
Been trying to get the bigger station modeules like garden, life support, but the time to collect the resources just takes awhile and only so much can do right now. Was hoping to have more station type rooms but I know it will come eventually. :)