I am working with the Perspective Dashboard component. As is, when in edit mode, if the use clicks on a cell, a built-in widget selector pops up automatically. I would like to be able to bypass that widget selector and have it instead popup my own custom widget selector.
Is there a way to prevent the built-in popup and have it pass that selected cell info to my own selector?
No, there is no way to configure your own Widget selector.
Even use of fancy CSS to "hide" the Widget Selector (incredibly dangerous because the required selector is very the very generic and widely-used div div.ia_componentModal) and modal overlay still leaves you in a state where you'd have to make use of the isEditing property to trigger a Popup of your own design - but even that would have no insight into the cell the user has selected. If you're willing to have the user select a location of their own through the Popup you could send a message to the Dashboard component, where it adds a widget based on your information in the sent message to the widgets list, but you run the risk of bypassing the inherent prevention of placing a widget at an occupied location.
TLDR: It's non-trivial and likely to break other parts of your project.