Basically, you should be able to tick a box or something when you go to make an engineering project and this will designate it as "Low Priority" or whatever language ends up being used for this. A low-priority project will never expire and so long as there are idle engineers and resources available, they will work on that project. You can have multiple projects and they will work on whatever is highest in your engineering project list that has available resources. The reason for this is that it would make certain mechanics in many total conversions much less tedious - examples include "cash crop" projects and loot boxes (Chateau de la Mort production/Casino gambling). Currently, you need to go and manually assign these projects whenever you acquire the relevant items, which is extremely tedious to do, especially if there is only one thing you want to do with them.
