Profile: David

Problem:
how to add default option to dropdown filter

Solution:
you can use the attribute default_label to add the defult option for your filtter.

You can find the proposed solution, in this case, with the following reply:
https://toolset.com/forums/topic/split-group-of-filters-with-parameters-on-archive-page-how-to-add-default-option-to-dropdown-filter/#post-1165434

Relevant Documentation:

Problem:
The issue here is that the user wanted to filter their map markers.

Solution:

What I would recommend that you do is to create a parametric search for this.
Take a look at this documentation below.
https://toolset.com/documentation/user-guides/front-page-filters/