Is there a way to group different taxonomy/content type in a single Select List (in a View)?
You can follow this using below step:


Go to Administration -> Structure -> Views
Edit your existing view or create new new. 
Add Filter for taxonomy terms you need
Click on "Rearrange" filter icon in Filter section
Click on "Create new filter group" and move filter taxonomy terms you need in new filter group. 
Select Operator as "Or" in new filter group and save the form.