An extension specialized to write multiple infinitesimal coefficients for the "diffcoeff" package

diffcoeff-multipledl.sty

\RequirePackage{diffcoeff}
\ProvidesExplPackage {diffcoeff-multidl} {2022/12/11} {1.0} 
  {An extension specialized to write multiple infinitesimal coefficients for the "diffcoeff" package}

\bool_new:N \l__multidl_isfirstdl_bool
\int_new:N \l__multidl_sep_primary_int
\int_new:N \l__multidl_sep_primary_default_int
\int_new:N \l__multidl_sep_secondary_int
\int_new:N \l__multidl_sep_secondary_default_int
\tl_new:N \l__multidl_diff_type_tl
\NewDocumentCommand {\mdlaux} {m} {
	\bool_if:nTF \l__multidl_isfirstdl_bool {
		\exp_last_unbraced:Nx \dl {\tl_use:N\l__multidl_diff_type_tl\int_use:N\l__multidl_sep_primary_int} {#1}
		\bool_set_false:N \l__multidl_isfirstdl_bool
	} {
		\exp_last_unbraced:Nx \dl {\tl_use:N\l__multidl_diff_type_tl\int_use:N\l__multidl_sep_secondary_int} {#1}
	}
}
\NewDocumentCommand {\mdl} {o >{\SplitList{,}}m o o} {
	\bool_set_true:N \l__multidl_isfirstdl_bool
	\IfValueTF{#1} {
		\tl_set:Nn \l__multidl_diff_type_tl {.#1.}
	} {
		\tl_clear:N \l__multidl_diff_type_tl
	}
	\IfValueTF{#3} {
		\int_set:Nn \l__multidl_sep_primary_int{#3}
		\IfValueTF{#4}{
			\int_set:Nn \l__multidl_sep_secondary_int{#4}
		} {
			\int_set:Nn \l__multidl_sep_secondary_int{#3}
		}
	} {
		\int_set:Nn \l__multidl_sep_primary_int \l__multidl_sep_primary_default_int
		\int_set:Nn \l__multidl_sep_secondary_int \l__multidl_sep_secondary_default_int
	}
	\ProcessList{#2}{\mdlaux}
}
\NewDocumentCommand {\setmdlspacing} {m m} {
	\int_set:Nn \l__multidl_sep_primary_default_int {#1}
	\int_set:Nn \l__multidl_sep_secondary_default_int {#2}
}
\setmdlspacing{3}{2}