In Magento 1 if I wanted to modify my own version of a phtml file I would move it into the theme directory, while maintaining the same structure. I have needed to do this on a single Magento instance that has multiple store views and uses different themes.
An example would be
Being added into
When viewing the website, my updated template would be used and not affect any other store views I have.
This method didn't require any xml updates, or technical wizardry, which suited me perfectly.
Magento 2 seems to be structure quite differently
The breadcrumbs file is held within
A slider file is here
Where would these need to be placed to display using my own theme, which is below
Solved! Go to Solution.
I don't know about your setup and different store views, but I overwrite core files simply by copying them into my theme with the same directory structure, replacing module-theme with Magento_Theme and so on.
So to change the module-theme directory, the directory would be:
Add subdirectories and .phtml files to match the original module-theme as needed.