Thing , Items , Bridges textual storage and it`s indication in WEBUI

Openhab-3.1.0M + JAVA-11 + Debian9
Is it right place to put this config file?

Why I can`t see it in WebUI?

Things files need naming in a xxx.things convention (not .thing).

Folder location depends on the way you installed, but should already exist and contain a readme.txt, so that looks encouraging. You could always read the readme, and see what it says about folder use.