It says on the tube not to eat it, not to feed it to your pets, not to let kids near it, not to use for tattoos... so it clearly is hazardous in some ways. It also says that it complies with ASTM D4236, meaning it has all the hazard warnings on the packaging... but I haven't seen an actual listing. If I were to guess, it may be just a somewhat toxic acrylic paint.

The main question though, is: can you convince your customs officer to let it through?

There are some levels of "toxic" allowed for general use just with the right labeling, some levels require being certified in handling and disposal, and some are banned altogether. It's also a changing target; for example, just in 2023 some regulation regarding hazard classes in paints and coatings has been amended, some types of glitter have been banned, allowed levels of VOCs have changed, and so on. I haven't seen info about when they got certified... because they got it certified, have they?

They do have a shop in the UK, but since BREXIT, that still means it needs to pass customs in order to get to anyone in the EU.