Whenever we want to debug an SPFx webpart on a site page we always search for the localdebug URL i.e.,
?loadSPFX=true &debugManifestsFile=https://localhost:4321/temp/manifests.js
and append it to the site page. Many times it is not very handy as the port number might be different and there might be additional query parameters appended to the URL.
I face this issue a lot which made me build a browser extension that will make this process easy with a click using SPFx Patron
Microsoft Edge Add-on /extension - SPFx Patron - Microsoft Edge Addons
Usage
Step 1
Open extension
Step 2
Check port number and click on the button "Load local SPFx files"