Hi @Anonymous ,
not sure, whether i got the problem: this sounds to me as the standard as it should be.
When you transport changes in a solution from one system to another, the things you transport are *added* to the existing things. So, if you transport contact i would expect the table in the targetsystem not to loose any fields (or forms, or views).
The major diffrence for me (i am not an expert in this field) between managed and unmanaged is, that managed solutions can be removed and the containd customizations are also removed. If you remove an unmanaged solution, you just remove the solution, the customizations will stay and you would have to remove them manually.
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Hoping not to have written too much nonsense 🙂 ,
Christian