This is entirely dependent on the engine, unfortunately, and ultimately it’s up to how it was implemented in the engine you were using.
The blending masking is handled by either a separate map or by vertex color/alpha. If you are using just a greyscale map or vertex alpha, you can only blend between two maps. If you’re using an RGB weighted map, where the red channel is the amount used for texture 1, green is texture 2, blue is texture 3, you can blend between 3 maps. It’s also possible to set up a sort of “levels” system, where say you have a greyscale map, and 0 is one texture, 64 is a second, 128 is a third, 192 is a forth, 255 is a fifth, and then blending between those values blends between maps, etc, but that is more difficult to use and limits the ways different maps can blend (IE texture 1 and 3 cannot blend together because 2 is between them).
Ultimately though, it depends on the engine you’re using.
Also, if you want to blend between multiple textures, you can always break up your geometry, so that you have part A blending textures 1 and 2, part B blending 2 and 3, part C blending 1 and 3, etc, etc. This allows you to blend with a greyscale between two textures but get more mileage out of the simple blend process.