Does Adobe Elements 2018 support Camera Raw of the Canon R7

No, not directly.

Take the time to read that faq:

https://community.adobe.com/t5/photoshop-elements-discussions/faq-will-photoshop-elements-work-with-my-camera-or-why-won-t-my-raw-files-open/td-p/4303022

Even the current PSE 2022  could not support it natively. (edit: it has been updated automatically last June).

So, the 'normal' solution for you would be to download the free Adobe DNGconverter mentioned in that faq. That standalone application can batch convert a whole folder your R7 CR3 raw files to the universal DNG raw format that your current PSE version can read and edit with the same quality.

There is another workaround :

https://helpx.adobe.com/photoshop-elements/kb/camera-raw-update-not-available.html

That would work with PSE2022 and some older versions, but I am not sure about PSE2018.

General rule: each new camera model comes with its own raw format which is not supported by previous versions of the converters (Adobe or third-party).