Does homeopathy work to cure or control svt?

None Known. There are no proven homeopathic therapies for svt.
Homeopathy does. not work to cure or control anything including superficial venous thrombosis (SVT). That doesn't prevent products or homeopathy practitioners from making claims, so the situation is "buyer beware". If you have questions about managing your SVT, talk with a doctor experienced with such treatment. Most family physicians & internists could help with this.
No. Truly homeopathic "medications" are made by repeated dilutions, so that the ingredient is not really in the medication anymore (just the "essence" of it remains). That means there is no active ingredient left to cause any benefit. However, that also implies that the homeopathic "medicine" should be pretty harmless, unless some other non-homeopathic ingredients were added.