Hey there @hossamzaio! Welcome to the community! Are the splines you’re intending to connect procedural/determined at runtime? Or are they put together in editor? If in editor, you can just overlap the portions and have the same node locations on each. At runtime, the idea would basically be the same, but if it’s a spline mesh that you want to blend, that gets significantly trickier.
A quick thread with 2 excellent resources for working with splines at runtime (or in general for the Epic tutorial):