Question

Hey, thanks for the great mod! I have a question. Is there a block that has the same shape as Framed Inverse Double Corner Slope Panel but is one single block (like how Framed Inverted Double Slope Panel and Framed Compound Slope Panel are the same shape, but the former is two blocks and the latter is one block)? The reason I want one is to fill a corner in a pyramid shape (attached image) in a way that would connect the textures.

The shape you are looking for currently does not exist. Compound versions of the flat corners for slope slabs and slope panels are already planned, so this addition definitely makes sense, I'll add it to the list of planned blocks.

As for the connected textures behaviour: as much as it may seem unintuitive as a player, this is expected because the connected textures system "sees" a very different structure compared to what you're are seeing. While you are seeing a continuous sloped surface, the connected textures system sees two regions of four cubes each which are on separate vertical planes:

Glad to hear it's planned!

Is there any way at all to work around the connected textures thing?

I did some experimenting, and I think slopes do in fact connect, but there is something weird about it.

On my initial screenshot, I mistook that gray line as block border; it's actually not. If I replicate the structure but remove one of the upside down slopes, this is the result:

So the issue isn't blocks not connecting, it's just using texture for the connected state of the block for when there is no block above, which is technically correct but not helpful. Can anything be done about this or is this just how connected textures be?

Shortly after posting this, I realized I can't fully connect non-corner slope panels either. Am I doing something wrong? I'm using a combination Framed Compound Slope Panels and Framed Slope Panels (Minecraft 1.21, NeoForge 21.1.128, FramedBlocks 10.3.1).

The result you are seeing after removing the upside down slope is the correct result, you should also be seeing that with the upside down slopes in place. For some reason the specific connected textures implementation being used there is deciding to connect to the back side of the upside down slope regardless. In that regard it would be useful to know which mod those blocks are from.

With respect to the missing connection: Unfortunately there is nothing that can be done about this as there is no way to trick the connected textures mods into thinking that the lower slopes are on the same horizontal coordinates as the upper ones.