Display custom toxicity in WordPress and the theme widget category selection drop-down list

is using a Premium theme, but unfortunately the developer has abandoned the theme. He's now broken with recent WordPress updates and worried about security risks, so I'm now trying to move on to another topic.

The problem is that the theme I am using is fortunately accompanied by types of personalized messages such as "Videos" added via the theme plug-in.

I am now having trouble creating custom toxicity
or categories so that CPT "Video" appears both in native WordPress widgets and in the drop-down list of categories in the new Widget theme. The only categories I get are only for default posts.

Any help will be greatly appreciated. I am not very familiar with php.