Forths do have local variables. (Cue debates on what makes a stack-based Forth-like language a "Forth".) Here is the description of Gforth's support for its own extended locals and the Standard Forth locals: https://gforth.org/manual/Locals.html (Cue debates on whether Standard Forth is a Forth and whether it is standard.)
When I learned Forth about 15 years ago, we used the { } syntax described here, not the newer(?) {: :} syntax: https://gforth.org/manual/Local-Variables-Tutorial.html