Could I get more details on the purpose of this canvas app? most WYSWYG editors are used to create templates/newsletters. 

If I can get more context on the need for an WYSWYG editor, i can work on this.

I'm not sure what is the use case of PCF control in this whole scenario. This whole requirement requires a model-driven app, command buttons, power fx, and power automate and mailbox integration.

In addition to above it require integration to PDF signing entities like Adobe e-sign

Need more details, On what hover does the image should show? hover on list of entities or a field? what image should shown? entity image or image from a website?