docs: 📝 Indicate where var dropdown is available

apps/docs/docs/editor/variables.mdx

@@ -47,6 +47,8 @@ To enable this, you just have to make sure that the variables exist in the varia
 
 <img src="/img/variables/declaring.png" width="300" alt="Iframe preview" />
 
+(This dropdown can be found in any place where you can add variables. It is global to your bot flow.)
+
 Then the values will be available on the Results page in specific columns:
 
 <img