In C99 and later you can use a similar workaround as JS/TS with designated initialization for functions which take a struct by value or pointer.

E.g. for a function:

    void my_func(const bla_t* bla);
   

It would look like this:

    my_func(&(bla_t){ .x = 123, .y = 542 });

Designators can be in any order and can also be optional (missing items are zero-initialized, so the function should be aware of that and replace them with defaults.

C++20 has a much more restricted designated init feature (basically useless for complex structs), but one nice thing in C++ is that default values can be declared right in the struct declaration.