To most common action that I perform is referencing items to each other (I don't use them as tasks). This suggestion extends the one posted a while ago concerning custom 'reference' or 'relation' fields. Apart from that, there is a need to insert links to other items (tasks) right inside the text field.
This could be accomplished by adding a button to the rich text editor 'insert clickup item link' or by rightclicking in the text field.
Another great feature that extends this functionality, is to make the clickup item links behave like youtube links...that users can choose to embed the task in the rich text area, for example by showing the first 50 words it contains, plus a link to that item.