Why have both `ds_save` and `comb_ds_save` in Tao>python beam?

Why does python beam have both ds_save and comb_ds_save:

https://github.com/bmad-sim/bmad-ecosystem/blob/112de1c70fab7504d0baea0ba35d98d0f156d865/tao/code/tao_python_cmd.f90#L338

Also, these don't correspond to any set command:

Tao> python beam
always_reinit;LOGIC;T;F
track_beam_in_universe;LOGIC;T;T
saved_at;STR;T;MARKER::*
dump_at;STR;T;
dump_file;STR;T;
track_start;STR;T;
track_end;STR;T;
comb_ds_save;REAL;T; -1.00000000000000E+00
comb_max_ds_save;REAL;T; -1.00000000000000E+00
ds_save;REAL;F; -1.00000000000000E+00
max_ds_save;REAL;F; -1.00000000000000E+00

Tao> set beam ds_save = -1
[ERROR | 2024-JUN-24 15:06:33] tao_set_beam_cmd:
    PARAMETER NOT RECOGNIZED: ds_save
    [DID YOU WANT "SET BEAM_INIT" INSTEAD OF "SET BEAM"?]

Tao> set beam max_ds_save = -1
[ERROR | 2024-JUN-24 15:09:32] tao_set_beam_cmd:
    PARAMETER NOT RECOGNIZED: max_ds_save
    [DID YOU WANT "SET BEAM_INIT" INSTEAD OF "SET BEAM"?]

Tao> set beam track_beam_in_universe = T
[ERROR | 2024-JUN-24 15:08:57] tao_set_beam_cmd:
    PARAMETER NOT RECOGNIZED: track_beam_in_univer
    [DID YOU WANT "SET BEAM_INIT" INSTEAD OF "SET BEAM"?]

bmad-sim / bmad-ecosystem

Why have both `ds_save` and `comb_ds_save` in Tao>python beam? #1015