To programmatically change the a block parameter you can use get_param and set_param to change parameters of Simulink blocks. The parameter you are looking for is MaxDataPoints. The following commands should get you what you are looking for.
block_handle = add_block('built-in/ToWorkspace', 'untitled/name1', 'Position',[0 0 30 30])
set_param(block_handle,'MaxDataPoints','inf')
Another helpful tip is after you add the block you have an optional output that would be the block handle. I used this handle with set_param to change the desired parameter. You can also pass this handle to the command inspect to see a list of changeable parameters
inspect(block_handle)
