Hello DuvE, great to hear from you!
At this moment ASE supports up to 4 Splats on unity Terrains, if you intend to use them on terrain we provide a Shader Function - Four Splats First Pass Terrain - and two samples - Simple Terrain and Terrain Snow Coverage - that show how to create a shader similar to the Standard one provided by Unity. As soon as we introduce Multipass, which is coming very soon, this limitation can effectively be bypassed.
You may also look into
Texture Arrays, which are often used in general texture splatting shaders that are not just terrain specific, such as MegaSplat. We also provide a sample for showing how to use them in ASE - TextureArray.
Jason Booth's MegaSplat uses specific techniques and optimizations that allow for using up to 256 textures, I can fully recommend getting it as it provides integration with ASE via specific nodes, so you're easily able to create compatible shaders while taking full advantage of his asset.
Please let me know if you have any further questions, thanks!