How is it possible to model one section of the mesh, for example the one I have selected in the Red rectangle, and to be able to affect other selected parts on the mesh (Blue).
You could do actions recording. Without using any addons, you could temporarily separate the areas you want to have modeled the same way by selecting each area in Edit Mode and pressing P > Selection to separate as new object. Then set the origin using RMB > Set Origin > Origin to Geometry. Then in Object Mode select all separated objects and press Ctrl+L > Link Object Data. Now you can model any of these meshes and it will get reflected to all the objects. Once you are done, select all objects and join with Ctrl+J then tab into Edit Mode and press A to select all faces then M > Merge By Distance to join all vertices together again.