This question came up in our group due to the interaction between floating disk and misty step. Floating Disk says:
If you move more than 20 feet away from it, the disk follows you so that it remains within 20 feet of you. [...]
If you move more than 100 feet from the disk (typically because it can’t move around an obstacle to follow you), the spell ends.
The question is, what will happen if you are using misty step while you have an active disk?
I suspect that how teleporting works is undefined, and thus up to the DM. In the absence of a statement that teleporting involves travel throught the etheral plane or somesuch, I'll rule that the disk follows you, as long as you do not teleport further than 100 feet away from it.
If teleporting however counts as leaving the plane, you would be more than 100 feet away from the disk while doing it, and teleporting would end the disk spell. Is there any description about what happpens when you teleport in some official source? I could not find any in the 5e core books, or in the SAC. Is there any in other publications for 5e, or in older editions that could be used as a fallback reference on what happens when you teleport? (I prefer 5e, but would be willing to use older editions as precedent).