I think it's important to define what it is exactly that you want to do. The solutions above work, but then it means that a manager can only every be part of one project at the same time.

What's more likely is that one manager may have multiple projects, and one project may have multiple managers. You can solve this in two ways in your domain model:

Create a many to many relationship between project and manager: 

• Simplified structure
• Easier to implement, especially for basic connections between entities

Disadvantages:

• Limited flexibility
• Difficult to store additional information about the relationship itself
• Can lead to performance issues and larger database size

Or instead, create an entity to link project and manager, such as Project Manager:

• More flexibility to store additional information about the relationship
• Easier to handle complex relationships with multiple attributes
• Can improve performance and reduce database size

Disadvantages:

• More complex structure
• Requires careful consideration of both current and future requirements
• Can be more difficult to implement, especially for advanced connections between entities

So to reiterate, your a many to many would look like Project * - * Manager

And the other option would look something like Project 1 - * ProjectManager * - 1 Manager

After you've done that, you can use various widgets like the combo box to do the actual linking on the page, but first your domain model should represent your data structure correctly.

Hi Priyanka,

You have to make one to many associations between project & managers and use AutoCompleteMultiSelect(download from mendix marketplace)  wid for selecting multiple managers.