You can have a content script detect the "save" action. Let's suppose it's a specific DOM element you know for sure it's going to be in the specific main, or that you create by yourself.
content.js
//content script
document.onreadystatechange = function () {
if (document.readyState == "complete") {
// Grab the UI frmo the mainpage you want to append the save functionality
var someElementsYouWantToAppendASaveButtonTo = document.getElementsByTagName("...");
var len = someElementsYouWantToAppendASaveButtonTo.length;
for (var i = 0; i < len; i++) {
// Create a UI save button to provide a functionality
var theSaveButton = document.createElement("button");
theSaveButton.value = "Save to Chrome Extension";
// Send data to extension when clicked
theSaveButton.addEventListener("click", function() {
var dataToSentToExtension = {...} // Retrieve from the clicked element, or whatever you want to save
chrome.extension.sendMessage(dataToSentToExtension, function(response) {
if(response.success) console.log("Saved successfully");
else console.log("There was an error while saving")
});
}, false);
someElementsYouWantToAppendASaveButtonTo[i].appendChild(theSaveButton)
}
}
}
Then, on the background, you detect the response and set up the popup as you wish.
background.js
chrome.extension.onMessage.addListener(function(request, sender, sendResponse) {
if(request.dataToSave) {
chrome.storage.local.set(dataToSave, function() {...});
// You can then set upn the proper popup for the next click or even switch to it
switch(request.popupToDisplay) {
case "awesomeDisplay":
chrome.browserAction.setPopup({...})
break;
}
var responseFromExtension = {success: true}
} else {
var responseFromExtension = {error: true}
}
});