Is there any native Mac OS X 10.15.3 keyboard layout that contains all ASCII characters plus č, ç, è, ǩ, ò, š, and ž?

Solution 1:

ABC Extended can make all those and more I think.

https://sites.psu.edu/symbolcodes/mac/codemacext/

but it's easy to make a custom layout with whatever you want using

https://software.sil.org/ukelele/