If every mesh you have is a separate object, this can get quite confusing.
You could join meshes with CTRL-J as already mentioned. The issue with this is that the modifiers linked to the object that is active when you perform the join operation will get linked to all the meshes you join.
A workaround that helps stay organised is to use Collection instances.
Select all the meshes that belong to one object and add them to a new collection. Name it appropriately. Then hide that collection from the render. Shift-A -> collection instance -> your collection. Now it appears as a single object and it easy to place. You can also instance it as many times as you want and all changes will be reflected everywhere.
To edit the source object, make its collection visible again and take it into local view to be able to edit it in a more focused and less confusing way.