There is a “ESP-IDF: SDK Configuration editor” setting to enable Long filename support.

Open menuconfig (see here for how to)

Component config > FAT Filesystem support > Long filename support

Choosing heap or stack to store long filenames?

Both are stored in RAM so arguably it doesn’t matter too much. A general guide though is the stack is generally used for storing small, short-lived variables such as local variables and function parameters, while the heap is generally used for storing larger, longer-lived objects.

So, unless you are keeping files open for long periods of time, the stack is probably better.