The first issue I see here is you have split the same resource as Resource A and Resource B to work for 50% in each project. Project doesn’t know Resource A and Resource B are the same resource and hence it can no way tell us if they are overloaded or not. Desktop Project doesn’t have feature to split the the availability of resource across multiple projects 🙁
The second issue is Project schedules the task based on when its predecessor task completes, and the working time of the resource. When Resource A and Resource B (the same resource) working on two tasks the work is scheduled on the same time. Creating link between these tasks will not be option, as they are independent tasks.
So, I suggest the following process 1. Don’t split the resource. Insert one resource and it will be assigned for all tasks 2. By default, Project checks for workload on day-by-day level. Since, you don’t want the work to be schedule on the same hour (or even minute), click Leveling Options in Resource tab, and change the “Look for overallocations on a” to Hour by Hour basis. This will alert the tasks that have resources who are given more work in the same hour.