Error-Notices in "Add new" and "Settings" page (and all backend pages)

When I look into the “add new”, “settings”, following errors-notices appearing:

Visual Editor – Add New (Image: https://nimb.ws/tC8wyq )

Notice: Undefined index: left_tag in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 560
Notice: Undefined index: right_tag in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 561
Notice: Undefined index: block_content in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 562
Notice: Undefined index: content-type in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 564
Notice: Undefined index: rich_editor in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 599
Notice: Undefined index: html_editor in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 600
Notice: Undefined index: icon in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 601
Notice: Undefined index: custom_icon in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 602
Notice: Undefined index: quicktag in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 603
Notice: Undefined variable: uploadfiles in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 632
Notice: Undefined variable: customicons in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 719
Notice: Undefined variable: customicons in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 763
Notice: Undefined index: styling_content in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 822
Notice: Undefined variable: post in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 1046
Notice: Trying to get property of non-object in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 1046
Notice: Undefined variable: count in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 1053

Visual Editor – Settings Page (Image: https://nimb.ws/ts60RH )

Notice: Undefined variable: count in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 108

Every Backend Page

Notice: Undefined variable: post in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 1046
Notice: Trying to get property of non-object in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 1046
Notice: Undefined variable: count in path-to-wordpress/wp-content/plugins/visual-editor-custom-buttons/visual-editor-custom-buttons.php on line 1053

The plugin works well, fresh installed (alone) on parent WordPress Installation. Only these error-notices are a little bit distracting.

Greetings,
Sascha

https://www.ads-software.com/plugins/visual-editor-custom-buttons/

Edited: Added “Every Backend Page and moved correct messages into it