With the arrival of the Gutenberg editor in WordPress 5, the ability to directly insert a WebHotelier Form inside your content via Gutenberg is readily available.
To find the block you have to search inside the Widgets subcategory. It is named “WebHotelier Form”.
Once you select it, you are able to override all the default settings from the sidebar at your right. Every change in the block’s settings will be immediately evaluated from the Gutenberg editor.